Big thanks to the folks who sent tips--they helped a lot.
Since everyone goes to Siem Reap, I'll start there - this town has become quite unpleasant in the 7 years since I was there last, but there's lots more good food. Favorite place was Khmer Kitchen, in an alley a block from Psah Chas--very homey, but with thoughtful touches. Excellent pumpkin soup; very good, thick though not stupendous chicken amok; surprisingly fabulous stir fried veggies, suffused with sweet roasted garlic that made them absolutely great; and yam "in oven"--chosen from a list of veggies described as "in oven"--turned out to be something your Khmer grandma would make you when you're depressed, an eggy, shredded vegetable casserole, not spicy or herbed, but very comforting and satisfying.
Also had some great dishes at the gussied-up Bayon. Very good beef loc lac--got the lime/pepper dipping sauce exactly right--and a rich, indulgent, sop-up-the-last-bit pork curry. Perfectly fine vegetables with ginger (Mom usually wanted this, so I asked for it in a lot of places, and was usually met with much surprise--was ordering in Khmer so it wasn't a language problem--they just usually seemed unused to the combo--maybe ginger usually overwhelms veggies so they don't do this?). Another night, I had to satisfy a craving, so pleaded for chhnang phnom pleung (not on the menu), and after much fussing about, they agreed. It's a plate of raw, seasoned beef (it may have been venison, come to think of it), with an egg yolk on top, and a perfect glistening white cube of fat with a dainty fork on it; and a dome contraption with hot coals under it . Grease the dome with the perfect cube o' fat, grill the beef and veggies, pour broth into the little gutters, put other veggies in broth. It was perfect. The meat had great seasoning (very reminiscent of the Muslim-cured meat in Yunnan), and the mushrooms grilled wonderfully. Left a big tip to encourage them to make this for those of you who follow.
Some good stuff at Arun--good amok, good pork curry, but an unreedemably dull, watery, inedible veggie soup (I knew it would be dull, but this was really bad). No high notes, but I'd go back. Wh'else, good homemade pasta at Red Piano--they've done a very good job with that place. Very good Thai at our hotel restaurant, Sawasdee Garden (Wat Bo Rd just above Rt 6). The owner is from Issan, so no surprise the chicken laap was very good. Also excellent red tofu curry, and nice snakefish with green mango sauce.
On to the provinces. In Kratie, we usually ate at the Mekong restaurant, which was always good, and had an excellent samlaw m'choo vietnam, as well as a good, but not as amazing, lemon-chicken sour soup. Heng Heng also had a good soup, I guess it was samlaw m'choo grueng (thanks to Michael Lerner for explaining this--see his posts below)--an intense pea green color, lots of trakooen (water spinach), and a very strong, intense citrus flavor. Stir fries at Heng Heng were fine but I thought Mekong was better. Fine morning mee noodles at our hotel, Santapheap, and okay coffee, but the one lunch there I thought very dull though my folks liked it. Be super nice to the waitress Dary, if she's still there--hard to miss, she's so earnest and energetic, really trying to work on her English. Good fruit in the market, where the old men still addressed me in French.
Adored Chhlong, further down the bank--no menu-type restaurants to speak of, but the place immediately next to the "port" (i.e., the small floating raft) had the best looking stuff in their pots, including a very tasty ginger beef, and were very quick about running off to the market for cold cokes for us and our motodops. Sweet people.
GREAT meal in Kompong Thom at the Sambor Prei Kuk restaurant, on the left immediately over the bridge from the center. Melt-in-your-mouth-tender beef loc lac (much better than the one in Siem Reap), a very zesty samlaw m'choo vietnam, fresh fish with ginger, fresh tasting trakooen. Poor Tiger girl, my stepfather doesn't drink. Adequate lunch at our I-could-be-anywhere-in-China Neak Meas hotel -- well flavored pork in the pork and pineapple, but dull noodles - no reason to go here when the other place is so good. There was a HUGE night market on with great looking food (remarkable emphasis on eggs), but I think it was just for the 7 January celebrations--live music, tons of stalls, anyone who is anyone in Kompong Thom province was there.
Sihanoukville--the French cook at Susaday, on Ocheutel Beach, knows his beef--ended up there 2 nights, both excellent (the wine sauce not so good as the meat itself) so long as you don't mind quite rare beef--the owner and chef here are very French, as are most of the folks who hang out there. Gorgeous views from Chez Claude, the restaurant menu didn't seem special, but a great place to enjoy sunset with a glass of good French wine if you want a change of pace from Beer Lao. Lunch was just mangoes on the beach--yum.
In Koh Kong, the potatoes at Otto's were wonderful (he's German, his wife is Khmer, both tastes reflected on the menu)-- order anything just to get the taters and the big helping of fresh veggies. He has a really nice place to relax there--all family run--good way to ignore the skeezy undercurrent of the town.
Fewer high points in Phnom Penh. Had a really nice first-night-in-Cambodia meal at Khmer Surin--very pretty place to relax. Followed the suggestions here, all excellent: the best fish amok of the trip, really good crispy rice cakes with a very balanced peanuty-pork spread, veggies with ginger The salad with chicken and banana bud needed a slight kick--maybe they dumbed it down-- but was still quite good.
Otherwise, had pretty good noodles and a good curry at Chiang Mai on Sothearos (hmm, hope they didn't suffer in the "spontaneous protests"), and was pleased to find that the apps at the FCC (for old times sake) were actually good--some good empanada thing. Meant to take the folks for fried sparrows, but instead we had to go to a birthday party for an 89 year old grandma, but got there too late and only had the soup (really good, delicate soup though).
Lastly, the restaurant at our hotel, the Dara Reang Sey (St 13 & St 118) (by the way, could NOT find La Marmite--definitely is hard to spot!), really surprised me by turning your basic pork and ginger stir fry into an absolutely amazing dish--pork crispy on the edges, ginger practically creamy. Also a good tom yum that helped clear my sinuses when I was sick, good morning coffee, nice morning rice noodles from the guy out front if I asked for vegetables (and they loaded them up), but the gray pork was weird and scary. Their prices may be a little high--say, $2 for the pork and ginger, but it was a lot of food. But great folks, great corner restaurant to hang out in and just watch Phnom Penh life go by. Main moto guy there--older, big guy with a helmet (yes, a helmet!)-- is very trustworthy should you be moving on at night.
Things I wished I'd eaten: frogs, Chinese noodles. Next time.