In my humble opinion, Cockos REAPER is the best digital audio workstation software out there for recording and mixing. It’s not the best for editing (use Audacity or Adobe Audition for that) nor is it the best for virtual instrument recording.
What I love most about it is that it rarely crashes, you can throw nearly any file format at it and export a wide variety of formats and it barely takes up any hard drive space. It’s low price tag is another great thing but that is secondary to its stability.
I started using REAPER back in 2009 after frustrations with Adobe Audition and Pro Tools LE. Cockos REAPER simply worked. I liked the default look of version 3.0 but if I didn’t there are a lot of custom themes that fellow REAPER users have created. It’s a VERY customizable DAW!
Enough of that, if you want to dive into REAPER for the first time then I recommend watching this video:
For more REAPER tutorials, I recommend the REAPER Blog and REAPER Mania YouTube channels.