The city itself is dreadful, don't go near it with a bargepole.
Honestly, I have been looking at the Białystok photo gallery online and the city doesn't look that bad. Many friends of mine have also been there and they liked the appearance of the city, mostly noting how clean it was with a mix of some interesting architecture. Some tell me it's an underrated city, on par with the likes of Katowice. Others tell me it's "undiscovered" and has plenty to offer. Perhaps I will go there some time and see for myself.