New Transmission add-on thread

i've just gone back to 1.7x and tried various versions, and im wondering if i have issues with my nas! i dont recall having high CPU time for aslong as i've used transmission... i could be wrong on that though.

ok, problems with 2.01 (also happens on 1.77betas, 1.93 and 2.03):
any form of active data transfer with from transmission causes CPU usage to be high.
this seems to cover both the initial annouce period, downloading and seeding torrents. however, idle torrents (sucessfully announced, but no leechers) makes transmission behave normally.
incidentially, i have similar high CPU time (although only briefly tested) on torrentflux and active torrents.

what could be the cause? hdd's not on HCL (although i have wdidle3 modded a drive)? nas issue? inherent torrent issue? the fact i have a low/under powered duo? or a bug?
come to think of it, i am seeing a higher-than-i'd-like network retransmit count, and network transfers a touch slower than i'd like too....