Ya, my only issue with Deluge is after ~500 torrents it starts to slow. I'm on private trackers, so I always tend to have ~2,000 torrents seeding at once. For my particular usecase, it simply becomes too slow and bogged down to be viable.
Granted, I've not used Deluge in some 2 or 3 years; maybe they improved process handling since then? I'd love to be corrected if so.