4.05 I think was the last version which did not need .net. And for what it's worth, 4.1 actually requires a Microsoft Beta version of 2.0.
IMHO, the drain going from 4.06 (build 1846) to 4.1 is simply not worth it. I have several tracks which stuttered when I had 4.1 on. I have since reverted to 4.06.
The resource issue is really one of hard disk and cpu. Not memory. If you've got your DAW stripped down, then 256mb is plenty. But you'd better have a couple of disks and a pretty decent cpu in any case -- especially if you're going to 4.1
My take.