The devices and ASIO drivers I use are: Presonus (FirePod) driver version 1.15.0.0 and Roland (Edirol FA-66, driver version 1.00. Both devices are firewire. I use them in conjunction with SONAR 5 Studio edition,
Notion 3, and BBW (since BBW version 2006 for Presonus and BWW 2008 for Edirol). These drivers run on a single CPU notebook (1.25 GB Ram, XP Professional) as well as a desktop dual-core AMD (2 GB memory, XP Media Edition). Latency is ~3ms or less with my buffer and sampling rate settings for either device or driver. I've never had an issue with either driver with any of the apps above. In both scenarios (but primarily the desktop) I use a combination of soft synths (built-in SONAR and also Dimension Pro), as well as Yamaha Motif Legacy and Yamaha rack ES. On the both units, I use hardware monitoring through either the Presonus or Edirol.

Other factors:

I have streamlined the settings in XP for both platforms, eliminating or disabling services I don't need. This makes a significant difference. I use ESET SS version 4 (and had used earlier versions) for firewall and Anti-virus due to it's small footprint and low overhead. I will turn it off if using several soft synths and more than 18 tracks.

Neither platform has networking enabled during audio sessions.

Additionally, I use the Edirol device and (updated driver) on a Windows 7 notebook (i7, 4GB memory, Windows 7 Professional).

Hope this helps