Having recently visited these places, I thought I'd give a quick update--
Las Delicias, a small Salvadoran restaurant in Lincoln Square is one of the best deals in the city (total bill for a very full meal, drinks, fried plantains for two was $13) and a homey and fun place, where the owner's daughters were dancing with guests in the restaurant and the smells from the kitchen are intoxicating. The main attraction are the pupusas, thick fried corn tortillas stuffed with a variety of fillings, each costing about $2; the best ones at Las Delicias are the fish, which have a bright orange fish filling; the blend of tastes between the corn tortilla and the fish is delicious. They also have excellent fried plantains, and provide spicy cabbage salad and and several salsas to complement the pupusas. (Las Delicias is on Western just north of Lawrence)
On the other end of the spectrum, went to Monsoon for a special occasion. This place does a lot with its decor on an "Eastern fusion" them but the bathrooms are probably the best part of the decor. On the other hand, it's very pricey--most entrees are between $20-28--and the food is uneven. I had a red snapper cooked in banana leaf, served with rice and a cilantro sauce which was very tasty although a little overpowered by coconut milk and cilantro; my partner had what the restaurant called a "vegetable napoleon" which consisted of paneer and vegetables arranged in a "napoleon" style which was OK but nothing great; for an appetizer we had a sushi-like raw tuna appetizer with a ginger sauce which contained a generous portion of tuna but the seaweed served with it was tough and overpowering. Overall, it was a good experience but way too pricey to spend my own money on (you're easily looking at $100/couple unless you order very selectively). (Monsoon is on Broadway just north of Diversey)
Dona Lolis is a Mexican restaurant in Rogers Park known mostly for its quesadillas, and they are delicious, especially the huitlacoche (corn fungus); we also tried the flor de calabaza, carne asada, and one other, but the huitlacoche was definitely the highlight of the bunch. It's a great deal, as enormous quesadillas are $2.50 each, and the restaurant is simple but pleasant enough. Since Dona Lolis has been discussed extensively on this board, I won't go on more, only to say that I think it's definitely one of the best Mexican on the far north side. (Dona Lolis is on Clark near Pratt)
Back to the other side, took my father visiting from out of town to Chilpancingo, another expensive pan-Mexican restaurant and Frontera spinoff. We had tostadas de ceviche for an appetizer, which were very good, and then had duck en mole and chilean sea bass as main courses. Both dishes were excellent, portions were substantial and the mole for the duck was particular smooth and delicious. It was also much more spacious and relaxed than Frontera, and service was much more pleasant and less snooty than Frontera, although not always so prompt. On the other hand, given the very substantial pricetags and my feeling that some of the ingredients used (especially the quality of the duck) were not quite up to Frontera's level, I was left wondering a little bit why it was quite so expensive. It's been a while since I went to Frontera, but a lot of Chilpancingo's entrees were $25 or more... I think I'd go back to Frontera again, although I have to say I've found Frontera's food inconsistent, and everything at Chilpancingo was consistently good.
(Chilpancingo is in River North, just near Reza's)
Other recent visits include Torajiro, a little Japanese place on Diversey, but I thought the sushi was rather tough and definitely not up to Matsuya or a host of other places; Edna's, a soul food place on Madison and Kedzie, where I have to say I was a little disappointed (I thought Sweet Maple Cafe on Taylor is a better breakfast place); and Tre Kronor, in North Park on Foster and Spalding, for dinner, where fish entrees, soups and desserts are worth a visit, although not quite as good as their breakfasts, which make them one of the best breakfast places in the city.