ATI X800XT-PE with Catalyst 6.1 on a very fresh install of XP SP2 (p4-3.2Ghz, 1GB RAM). WB5 works fine but slows my desktop way down. Happens with all skins that come stock. Tried WB v5.00.01 and b.011. I used Passmark Performance Test 6.0 to come up with differences:
Benchmark no WB WB5
----------- -------- -------
2D Lines 118.76 7.25
2D Rects 89.54 54.48
2D Shapes 7.90 3.46
2D Fnts/Txt 168.04 71.34
3DWin Simp 2014.39 9.39
3DWin Med 350.54 17.92
3DFullScr 32.41 32.41
I don't know what all the number mean precisely, but I can replicate them on demand. In fact, no tweaking I've tried within WB seems to make more than 5% difference.