I use Steinberg Cubase 5 and Propperheads Reason 5, I primarily use Cubase as the main sequencer and have Reason rewired, why?
Cubase has a very good sequencer, much better than Reason in my opinion, and I also like to have a large variety of synths and effects etc that can be added to Cubase from third party developers. Ther other main reason for using Cubase is the fact you can import, record, and edit audio easier, as I do not have Reason Record. I do regularly use Reason as a stand alone DAW for the start of tunes and some basic sequencing, its great to load up and instantly start creating music and getting ideas with, but once i have a few ideas i normally revert back to Cubase and export MIDI into Cubase again. The great thing about Reaon is its reliability... very rarely crashes unlike some of the other DAWs out there.
I have used nearly all the DAWs out on the market, as we had to use many different ones on my Music Technology course at Uni, and I still feel most comfortable using Cubase.
LogicPro is also a very good DAW, although I do not own a MAC so that one is out of the question, but even if I did I would still use Cubase, I just prefer the way it works, and I have been using it for about six years now! Some of the effects and synths in Logic piss all over it competiors, so welll worth a look if you have a MAC!
Pro Tools is great for editing audio, and I mean really great! The only thing that really lets it down is the use of MIDI, the MIDI engine in Pro Tools sucks ass, or it did in version 8, not tried any of the updated versions. Editing MIDI along side audio would often cause things to become out of sync... which is not what you want when trying to make music, and would also often lead to crashes!
Ableton, nerver really used it to create music with, but I do use it for DJ sets, great for time-stretching, creating loops, mash-ups, and has some great effects, and when paired with some of the MIDI controllers out there becomes a whole lot of fun!
Never used FL studio, so cannot really comment on it :-/
In my opinion Cubase is a good all round DAW and getting better with every update, the only real downfall is some of the synths included with it are not that great, and therefore third party developers are probably a must, unless you rewire with Reason and become a "Thor Whore" LOL