Where can I find reviews on a building/landlord?

It's not reviews per se, but you can often get a good sense of how a building is managed by looking at publicly available complaint and violation data. Look in city records: BISWeb, DHCR, etc. Nearly all buildings will have a few complaints, incidents, etc. but if well-managed they won't have too many and the records will show them as closed out (which requires some paperwork, administrative tidying-up type work with the city agency) rather than being left open.

Through our purchase process we painfully learned that those sites are limited in information. Your best bet is to talk to well established, reputable brokers. Another good resources is this site (Streeteasy.) For example, we had an awful experience trying to buy into 230 West End Ave. We were strung along for months by the board and seller. We thought we had done our homework but after having a very positive experience later on which ended up in a purchase, we realized that an experienced broker makes ALL the difference. Good luck.

This would be really helpful. I find though that most reviews are from the bitter people who havan axe to grind, like they wanted something outside of the lease and were told no or that there is a cost. Or they were below market and suddenly the landlord wants to get to market and their good deal ran out so it is the landlord's fault. Such is life - it applies to all sorts of retailers and service providers.