WB 4 isn't likely to come out this year but the betas for it will.
And even with the current internal alphas, I think it is safe to say that WindowBlinds 4 won't just be faster than msstyles on any hardware, it'll be so dramatically faster than msstyles on any hardware configuration (regardless of video card) that there won't be further debate on it. WB3/msstyles will feel painfully slow compared to WB 4. In short, there should be no more "YMMV - your mileage may vary". No matter whose machine it's being run on, fast, slow, whatever, WB 4 should appear faster to the point that they notice the difference fairly quickly.
It'll also be equally as compatible as msstyles thanks to new XP APIs Microsoft put in that we are going to be using. Let me give you an example - those apps that put their own buttons on title bars - they'll now work. Their button will show up on the title bar.
I won't touch on the actual new features of it until later on, but we think you'll find them equally cool.
We still have more versions of WindowBlinds 3.x to come out. Skincast is due in 3.5. The task pane won't get into until 4.0 though since we can't just read shellstyle.dll since that's a copyrighted DLL.