EDIT: this seems to be solved.
I found this post on the utorrent forum
It's known issue, try to set net.low_cpu = true in Advanced section of uTorrent's preferences.
I still see some small spikes up to 10% but I was spiking between 50-70% or more with average around 30-50%.
I am running utorrent v 2.2.1 build 25302 (last build before 3.0) on windows home server 2011 (custom built sempron 2.8ghz with 4gigs ram). The other day I noticed very high cpu usage from utorrent. like 70-80%. it is only happening when downloading not uploading.
I followed the instructions under best practice tips For fixing CPU-load/memory-issues/Disk-verhead/stability found here:
http://forum.utorrent.com/viewtopic.php?pid=480554
It seemed drop usage about 10% but that still put me at around 50-60% cpu. I have no av other than the built in windows defender. I disabled it and peerblock and it seemed to also help but not cure it. I'm now spiking around 50 with average 30+!
I use the same build on three machines and the home server is the only one effected. the server acts as my media box so I can't afford for so much cpu usage nor is it normal! I tried the build below it with the same results.
ports are forwarded properly. I have 30/5 service so speed isn't an issue. utorrent is just sucking up tons of my cpu!! I use stable bit drivepool. it happens when downloading to pooled drives as well as my unpooled d: drive. I disabled search and indexing on all drives as well. can not figure this out!