REAPER is a digital audio workstation: a complete multitrack audio and MIDI recording, editing, processing, mixing, and mastering environment.
For starters, REAPER is coded by a small group of dedicated engineers, not multiple software units under the central command of product marketing. That means REAPER is lean, efficient, and stable. REAPER starts up and is ready to record in seconds, balances processing loads intelligently across multicore systems, and doesn't fall over when you start to tax it. That means you spend more time recording and editing, instead of staring at the startup splash screen.
REAPER also gives you two major version updates with your license. And we don't parcel them out once every year or so, either: REAPER is famous for its fast, frequent, and most importantly, stable upgrades. If you had bought REAPER 1.0, you would have received over 250 free upgrades, all the way to the end of the 2.xx version series, and the application you had at the end of the license period would have had far more depth and power than the one you started out with.
Much like video editing systems, the tools for crafting, mixing, and multi-tracking digital audio projects - be they music, audio or sound for video endeavours - have reached a very mature stage in their development and evolution as technologies. The Digital Audio Workstation (DAW) market has grounded itself in all-digital workflows and common production practices whilst, at the same time, diversified into an array of major players. Each major software DAW has its own strengths and weaknesses, each has an established market share and there is consistent (albeit too often tentative) innovation pushing ever forward.