The workflow alone had me sold. In addition to the audio playback engine being very smooth (the ability to add/remove instruments and effects with no audio skips or pauses made me fall in love).
I've been using S1 since right before 1.5. It's gotten significantly better with every major upgrade, to the point where you can now do pretty much anything you need to do in S1, from conception to selling music. Couple that with things like
Melodyne integration and wow.
The stock instruments are one of the weak points IMO. However.. you get some decent third party sounds to go with it. Softube saturation knob is also free with S1 (hopefully you can still find the promotion for it).
The other other weak points to note at the moment are that S1 doesnt have a great Mackie HUI implementation, so some of the expensive control surfaces are not well programmed with S1 without some user tweaking needed. It doesnt have much video editing capability, other than basic video playback thru its quicktime wrapper. Doesnt have super
advanced midi options (but what it does have is more than enough for me. People complain about it not having midi effects and things of that nature.... i dont really care.. there are workarounds that feel just as simple). no bitbridge (however... bitbridges really suck anyway... just go full 64bit and be done with it).
I say the bove ust to be obective... but at the end of the day... none of that was a dealbreaker for me. i personally think its the best DAW on the planet. Only one I havent tried is Logic bc im on PC.