If you put in a pattern and it doesn't cover the whole measure don't sweat it. Most patterns in session drummer are still on the beat. Sometimes it's those slightly irregular patterns that sound better for fills anyways. I have been known to chop up fills and do some splice work until I got something I liked as a fill,or use the PRV, maybe add a few extra hits or a crash right where you want it to be. Not difficult to do with a cheap midi controller.If you have a Roland drum set man you have it made.You can use a 120bpm fill in an 80bpm track it will simply be slightly slower.
I have heard the work from some others done with only Session Drummer and if you hadn't told me it wasn't something else I would never have known. You can make killer tracks in it. I have a project I'm working on where I used some of the midi in Session drummer and then I used a second well known drum program to compliment it. Like having two drummers that play well together.
I think a lot of the material in Session Drummer is pretty decent, especially for a program that came as part of X3 and to top it off, how many DAWs offer two pretty nice drum programs with their DAWs as part of the deal?
I'm just trying to find out a way to switch my drum soft synth after I load one of those nice free templates for Session Drummer ;)