First off, anybody dismissing this great piece of software as a toy is on some weird, gear-snob trip, and couldn't make a decent tune with a roomful of Access, Waldorf, and Novation gear. Reason is hands down the best bang-for-buck piece of software around. It's also the most-user-friendly. If you're just starting to make music on the computer, start with Reason.
Reason is primarily a dance music tool, but there are enough decent acoustic drum (except cymbals) and instrument (except guitar, but whoever uses guitar samples should have their head examined, anyway) samples in the Factory Sound Bank to create virtually any kind of music.
Another great feature is that just about everything can be automated: from all parameters within the modules, to the volume, panning, and effect levels of each track in the mixer. Also, you can export either loops or the entire song as a .wav file, which you can obviously then edit in Cool Edit, Sound Forge, etc.
Reason is greater than the sum of its parts, partly because it’s so easy to use, and partly because it’s so convenient to have basically an entire studio right there in front of you, where you can freely add as many components as you want/computer will allow (and it’s very easy on the CPU: I’ve got a PIII, 800mhz, 512mb of ram set-up, and I literally can’t max out the CPU usage). The SubTractor synth isn't as beefy as some of the better VSTis out there, and the NN19 is a limited sampler, but ReDrum is fantastic, and easy to use, and you can import ANY sample in wav or aif format into it. The Matrix pattern sequencer goes a long way to help contour your sounds in a more expressive way, as well.
The interface gets a 10, but the actual sounds in it get a 7 1/2-8, so that's basically a 9. Get Reason, ESPECIALLY if you're just starting to make music on the computer. If you're using Cubase/Logic, and have a nice selection of VSTis, and everything's running smooth on your set-up, you can pass on Reason, but otherwise, it's a steal.