2.1.1 will probably be released next weekend, gonna include some more bug fixes this week.

I'm not able to reproduce this high CPU usage, even with an old laptop, things seems to be going pretty well when limits are in place.

What kind of traffic limits did you have set ?

I've turned off the download limits, I have my upload set to 30KB/s, I have a ton of torrents queued for seeding, a few downloading and 9 seeding (only about 2-3 are ever actually uploading at any given time, or 0, the downloding torrents usually take priority for some reason), 1024 max connections, 128 max per torrent.

I used to have it higher, but I assumed lower limits would help cpu usage.

I´ve noticed this high CPU also. KT 2.1.2 takes about 22-30% CPU on a 2GHz Celeron (showed all total 4 torrents). If i switch to an empty group, KT reduces to 9-13% CPU.
Maybe this can help the devs to reduce the CPU-usage in future versions.
CU

GUI updates take time obviously, however you can tweak the GUI update interval in the preferences dialog, setting it to 2 seconds will cut down CPU usage.