I'm currently evaluating Reaper as well. I have Cubase LE 4, and have invested in Addictive Drums, Amplitube packages and some SampleTank stuff. Everything *works* in there, but for the simple limitation that I can't route MIDI tracks into sampletank to use multiple channels as inputs.
I spent about 2 hours w/ Reaper and was able to get a set up almost identical to my LE4 personalized templates, and all my VSTs and VSTis load so far. I'll be tackling the SoundTank routing tomorrow. If all goes well I'll be a convert too!
I'm looking forward to having a stable DAW that I can run on my PC at home for personal recording; as well as my MacBook to work on my current band's first batch of original recordings...