I'm firmly in the play-what-you-feel-at-the-moment camp. I just don't see the appeal of playing the same songs identically over and over.
(Then again, the note-for-note thing works pretty well for Neil Peart!)
I've always been in the above camp but recently when I've been listening to songs that I've played in covers bands in my mind I'm playing something different to what I actually play and in my mind it sounds a lot better.
If listening to a song and imagining what I'd play with no restriction I'm the best drummer in the world ................ I did say in my mind
now take some of those amasing fills and make them real rather than imagination.
I'm about to try a project and spend at least 15 mins of each practice now working out the fills in my mind and putting then to the music to see if given a reasonable period of time like 6 months it actually makes me a better drummer or detracts.
I also wonder if it'll help me start using my vocabulary a lot more, there are so many fills I've learnt practicing but just don't use when I'm playing and I think it will work them into the music so they become a lot more natural and I'll start using them on a more regular basis in other songs / my everyday playing as I get used to using them.
My thinking behind it you have good days and the bad days when you just don't "feel it" it'll have a bigger impact on improvisation than something practiced.
Be really interesting to see what others answers are generally but I'd love to know what Bonham, Billy Cobham, Aaron Spears, Gavin Harrison, Dennis Chambers and Simon Phillips answers are to name but a few and if they're the same as Neil Peart's who lets face it isn't that bad when he has a good day