Just returned from a slow crawl through the year-old Culinary Delights in Natick, a Russian (with a little Jewish, Polish, and a tiny bit of German stuff thrown in) deli/specialty store/caterer. I haven't been to Berezka, so I can't compare, but this place is definately a Metrowest plus. Smoked fish of several varieties are of excellent quality. Frozen varenekis, cherry-filled "Russian Ravioli," and more from Oceanview Cafe in Brooklyn are quite good. Frozen sour (I assume) cherries. Russian dairy products, kefir. Store-made specialty items like garlic beef aspic (don't remember what it's called), perogi (baked), cabbage rolls. Kasha, millet, cheap bay leaf. Lots of relishes, honeys, preserves, etc. Space is clean, sunny, and well-organized, the people are knowlegable and helpful. I plan to be a regular.
229 N Main Street (Rte 27 just north of Rte 9)
Natick - 508/653-5553