I have used Cubase (although not recently), ProTools (I own PT10 and still use it from time to time), Fruity Loops (I own this one), Reason (I own this one, too), Cakewalk (long time ago), and Reaper (which I have used since May). I originally got Reaper as a demo to check it out, and as an alternative to the upgrade-aholic and CPU hog (at least on a Windows machine) ProTools.
My other programs rarely get used anymore because Reaper is amazing and THE most computer efficient DAW I have ever used. It uses a fraction of the computer resources that ProTools does (I have done head to head tests with songs), it loads super fast, and it rarely crashes (unlike ProTools). There is nothing I ever did in ProTools that I can't do in Reaper, and Reaper is a lot less finicky about my old plugins than ProTools which is important to me because I can't afford re-purchasing plugins. It runs the latest VST plugins (ones I have bought within the last 6 months) perfectly as well. I used the demo for a month, and went ahead and bought it. I have never looked back, and I love it (yes, I am a 'fanboy' lol). The configurability ROCKS, and the price is incredible for such a powerful DAW.
In a nutshell, it is perfect for a guy like me with a project studio who likes the flexibility and price (I can spend those dollars somewhere else now!) of Reaper. Do not confuse Reaper with some scaled-down 'affordable' DAW you settle for instead of ProTools or Cubase. It is every bit as top notch as those DAWs. It is a little intimidating at first but it doesn't take long to get a handle on it and then you just keep learning more (just like with any DAW) as you use it. I have never been more productive churning out music.
Just my 0.02
Peace,
TC