Thanks everyone - also for the additional postings around bitflipper's subtopic.
Cactus, most versions are available in 32 and 64 bit versions, each having different sizes. Only 2.01 is 64 bit only. Only 1.00 is 32 bit only.
Release notes only went up to 1.03, as you point out.
I just re-read some.
For example, the release notes for 1.02 mentions improving latency on windows. I wanted that.
They also mention fixing an issue where "some machines develop periodic noise after more than 1 hour", indicative of a memory leak. I didn't want that!
So I always felt getting the latest is the right thing to do.
Anyway: I shall re-install the original 1.0 drivers this weekend. Trouble is, I'll only really know they're stable during a session or two, so that'll be Thursday.
If I have a failure, I shall go back to WDM.
Here's the link to drivers:
http://tascam.com/product/us-1641/downloads/ There are audio drivers AND firmware updates!
I am waiting for the first user reports of the Roland Octa-Capture. Depending on price drops, ease of use and reliability, I shall start saving for two (they supposedly can be used in pairs, giving 16 XLR-Ins.)