Been a bit since I tried: has valve done anything to improve the bot situation, or is the game still unplayable?
Last time I tried to play; I got into 3 games over 2 weeks that weren't already infested with aimhack bots; but you had to be ontop of constantly vote-kicking the bots that did join every 2-3min.
It's gotten a lot better. I've been getting back in to the game with some friends of mine lately. We do encounter bots every now and then, but one of two things happen. Either it's a single bot that's kicked pretty quickly, or a few bots join at once and we just queue up for another server. Either way, it doesn't happen that often and we can still have a good time playing in pubs. If you play community servers, bots are basically non-existent. Definitely worth giving it another shot if you're at all interested in playing again, the new summer update just dropped a few days ago!
I played a bit a few weeks ago and I didn't have any issues with bots but the last time I played for more than 1 day was years ago so maybe I just got lucky :p