I've sort of been following the development of
Reaper for the last year by checking it out every now and then. It seemed like a good idea as the aim was to make a very efficient and lightweight DAW without all the code bloat.
The first few times I tried it, it seemed a little rough, and the GUI was just brutal (unless you liked Windows 3.0 of course).
But I just installed the latest version on my laptop to play around with it, and was blown away with it. The GUI is now customizable, and it seems very stable. It takes a little getting used to the "minimalist" approach, but I'm really starting to like it.
The feature list is very impressive, and the funny thing is that it already has a lot of the key features that I have been waiting years for Steinberg to include in Cubase SX.
Here is a screen capture after I combined a couple of supplied themes.

It's only a 1.8MB install, and is definitely worth checking out if you're on Windows.
JL