Here are the figures for the last 30 days for one of my machines using a Xeon E5410(8 cores) with Linux Mint 64. These are all DSFL units. I averaged about 50 WU per day. There is some variability, but overall not too bad.

Date Average Time in Hours
5/28/2013 2.8765
5/29/2013 2.8688
5/30/2013 3.1899
5/31/2013 3.1610
6/1/2013 3.0734
6/2/2013 3.1533
6/3/2013 3.1952
6/4/2013 3.1624
6/5/2013 3.1872
6/6/2013 3.2658
6/7/2013 3.0801
6/8/2013 2.9187
6/9/2013 2.8130
6/10/2013 2.9240
6/11/2013 3.0238
6/12/2013 4.9184
6/13/2013 4.0429
6/14/2013 2.9492
6/15/2013 2.7898
6/16/2013 3.9743
6/17/2013 3.6720
6/18/2013 2.8493
6/19/2013 3.3989
6/20/2013 3.3890
6/21/2013 2.9641
6/22/2013 3.9227
6/23/2013 3.1796
6/24/2013 3.1833
6/25/2013 3.1852
6/26/2013 4.3571
Cheers