I use FL Studio, Guitar Pro, and Sony Acid.
I got into FL Studio around six years ago, I was fourteen. This is when I really began to understand and develop a real feeling for music due to my rapidly progressing skill on the guitar. I had also just discovered Newgrounds about a year or so earlier which broadened my musical interest. At the time I conclusively decided that trance music was the bee's knees and had to produce it non-stop forever. I began reading description of the tracks, forums, news posts, and watching YouTube videos to figure out what the best DAW would be to start with. Obviously FL Studio was a reoccurring application, thus, in my naive mind I thought it was the best.
Guitar Pro is something that I came across when I first began playing guitar a decade ago, I couldn't figure out a good way to learn songs without listening to them repetitively, and even then I would get lost trying to follow along with the tablature. I came across something called Guitar Pro while I was on Ultimate-Guitar.com, decided to Google it for some information and found TuxGuitar, which was my free substitute up until last year when I finally made the purchase for Guitar Pro 5.
And finally, Sony Acid Express was the first program I had ever come across for live recording. This was also about eight to ten years ago when I was just getting into guitar so I didn't think there was anything like Logic or Pro Tools that could possibly exist. I hadn't even heard of FL Studio at this point. Anyway, I began using Acid Express to record little riffs and licks for a couple years before suddenly never touching it (also known as the time I discovered FL Studio). A couple of years ago, I decided to try my hand at recording guitar again and purchased the latest in the Sony Acid line of recording software.
What it all comes down to is; I use the software I started with because it's where I'm most comfortable. If you have me open up Pro Tools, Logic, Ableton, Reason or whatever, I won't know the play button from a synthesizer (not true, maybe).
Sorry for the long ass post.