I miss FL Studio too..I switched from PC in April, but I don't regret it one bit.. Unfortunately, there is no FL for Mac.. I am hoping the will release a version soon.
Anyway, you can run bootcamp so you can still use FL Studio on the Mac under the Windows platform. If you are like me and don't own a copy of XP, then you can obtain Reason, or Ableton Live. They have sequencers similar, and some may argue even better, than FL.
I used FL for about 6 years, so I am very used to the program, but I've found ways around it. Started using my triton more for sequencing, and GarageBand is actually becoming more appealing to me everyday. If you have GB 3, load up a Sound Effects Software Instrument, and change the octave range by pressing z or x, and you have all those keys you can fill with your own drum samples! You just click and drag to the key! You can even step edit to quantize.... It's just a matter of finding a new program and getting used to it, or run Bootcamp...
But I feel ya on that..long live FL Studio...