3.3.12 on windows 10 with 8GB RAM. Current uptime is 68 days for both the PC and qbittorrent.
Startup and shutdown of qbit is pretty slow with 15k torrents if using HDD: 15-20 minutes to startup and 10 minutes to close but I shutdown so infrequently it isn't an issue. Running it on an SSD and startup/shutdown times are reduced to a minute.
I don't have torrents set to autostart so never had it download anything automatically but a couple of times I've had it tell me files were corrupt/incomplete upon startup. Usually a recheck takes care of it but once the files actually were corrupt and I needed to redownload part of the torrent.
Overall no bigger problems than I've had with any other client I've tried.