No - running @ about ~30% CPU utilization, with ensign, excel, IB sludgemonster java, and camtasia.
excel is taking about 15 mb of ram
P4 2.3 GHZ, 1GB ram, 256mb gfx
The only thing I noticed was when it stops updating - lower left hand corner hangs on "calculating cells 0%" but it seems to be related to moving other windows across it.