A digital-audio workstation is probably the most important purchase an audio engineer has to make--it's the command and control center for your entire computer-based recording rig, and you'll be spending most of your time in it.
Unfortunately, pro-level DAWs are complicated pieces of software, and everybody's got their own opinion about what's best--ProTools is widely considered the industry standard, but I know several experienced engineers who don't like it at all.
Because of its complexity and importance, choosing a DAW is not the kind of decision you can make from reading reviews alone, or even from talking to fellow travelers. You need hands-on time.
That's why Cakewalk has released a free 30-day trial version of Sonar 8 Producer Edition, the newest version of the company's high-end DAW. (Cakewalk also makes a wide array of audio-recording and manipulation software for consumers.) It's available for both 32-bit and 64-bit versions of Windows XP or Vista (Mac users need or another Windows emulator). Recordings made with the trial version can be saved permanently.
The download is here.