We've been focusing our efforts so much on making WindowBlinds 3 faster than Luna on XP that we've not really talked about all the new features in it.
Here's a link to the guide which goes over tons of things that are new in 3.0:
https://www.stardock.com/products/windowblinds/wb3/wb3_guide_final.htm
A few goodies include:
1) An inclusion list. You can now say "I only want these apps skinned, leave everything else untouched."
2) Ability to use the Start bar from one skin in all your other skins.
3) Can now change the fonts in your title bars as well as modify colors on the fly on the system.
4) SmartBars. Instead of the skin author saying "This is a roll-up button" they put "This is a Smart button" where the user decides what type of button it is.
5) Hyperpaint. We can now use unused video memory to accelerate windows painting. If you have XP, try this, on reasonably small windows it completely eliminates repainting which makes moving windows much faster (something very important to us software developers where in WB2, its performance hits over classic were always a big negative when you wanted to use its extra features like always on top and such).
6) Auto-theme aware. If you use Windows XP, Luna (and all other visual styles) only does title bars on non-theme aware apps. WindowBlinds 3 can skin them all completely (full version anyway).
7) Ability to change the painting method. In WB1/WB2 you were stuck with a single paint method which might be fast or slow or buggy dpeending on yoru video card. Now you can choose DDB or DIB paint.
8) Cleartype font support in controls on XP.
9) Native Vector Format. This isn't documented in 3.0 but it'll be documented as soon as we can. Basically vector based skins. I don't think one needs to talk about too much what the advantages of vectors over bitmaps is.
Coming in 3.x soon:
More stuff in on the way:
a) Skincast. A quasi-peer file sharing thing where people set up their own skin stations that people can subscribe to.

Tons of new skin controls. You know the cool stuff DesktopX does right? Well, not only will you get to have mouse overs on all sorts of new controls but ANIMATED mouse overs. Remaining controls, even obscure ones, will be able to be skinned.
c) More sound support and tying it into mouse events (so when you click on that radio button you can hear a click if you want).
d) UIS1++. UIS2 is already faster than Luna but it is slower than just runnign classic. UIS1++ isnt' as powerful as UIS2 but it can handle many of the most popular skins and its speeds should be more closely related to Windows classic. Our goal is for WindowBlinds to be more than just a skinning program but a GUI acceleration program.
Speaking of GUI acceleration, take Hyperpaint for example. Right now, there is a limitation on memory bandwidth. The size of the window it can accelerate is dependent on the # of bits (so a 16bit color window can be much bigger). But as video cards advance, eventually full screen windows will be accelerated.
Imagine that - complete elimination of repaints. Similarly, DirectX features (DirectX 8 and later) can be used more easily in 2D which we plan to do for increased performance.
The goal is to provide for a completely customizeable skinnable user interface that is as fast or faster than a system without WindowBlinds. With WB3 we've worked to make it slightly faster than Luna (msstyles) but over the coming year the gulf in speed between WB should increase as more acceleration is put in.