DETTO Transmission went unusable for me since 1.5x. In 1.60 it's still a whole mess for me.
The problem: I start more then one (lets say 2) downloads. Both of them are folders which contain several files. Transmission connects to peers, starts downloading, speed goes up to about 400,500,800 KB and so on, and then suddenly hangs/stops for a sec or a bit longer (and it's not just the GUI, I checked the network bandwith with iStat). So after this 1 sec or bit longer Transmission asks the connected peers again to send data and begins downloading. Speed goes up, data is written to HDD, Speed goes up even more, and bam, again a hang/stop. It's damn annoying, pretty agressive to the connected peers (this though is just a guess) but most of all just unbearable for a torrent client.
I hate to mention it (because many of you don't like it, its a port and so on) but uTorrent has no problem with that. I think it *peep* in features and ease of use and everything, but at least it gives me my maximum download speed and it has absolutely no problem with writing much data to HDD or hanging/stopping.
(Version 1.60)