Reason is my drug of choice . . . but I also have taken advantage of Cubase, ReCycle, Re-Birth, ProTools (Free), Absynth, Metasynth, Spark, Peak, CAPS2MIDI, Goldwave64 (PC), Little Drummer boy (PC), and Stomper Ultra++ (PC); All of which have been very useful programs.
They all have there advantages and disadvantages, but you can create music with any combination of these programs. Reason is only prgram where you can have a virtual mid range studio that lets you create as much music as you want, with as many compenents as you want, straight outta the box (and can be expanded by samples that you have or make and also by programs like, ReCycle, Re-Birth, and Cubase.
I've been wanting try Neuendo for awhile, but haven't had the chance.
if you're into drum programming and using loops then reason is the stuff ( and its only $250.00 and you don't need I/O gear).
if you want to record and do just minimal midi stuff then protools free is cool. if you want to do more than just 8 tracks of audio and need serious midi strength then digital performer, cubase or logic will do the trick. if you get one of these three, spend an extra $74 and get cycling 74's pluggo plug-ins. an amazing value and you can create some seriously twisted audio with them.