I have KNP, TGF, MMF, MMF1.5 and the MMF2 demo version, and well, I still use TGF.
I really don't mind any part of MMF other then the animation editor; tgfs is just plain better. No going back.
MMF2 takes what people originally hated by MMF 1.5 compared to TGF, and puts it in. I really don't see why people still prefer TGF over MMF2. MMF 1.5 was chunky and overcomplicated yes, and unstable, again, yes. MMF2 is much better in every way, then TGF though.
I still use TGF, old habits die hard and I just find it so much easier than anything else tried mmf 1.5, mmf2 and tgf2). Going back to KnP is really tricky though.
Personally though, I find MMF2 a bit crowded on anything lower then 1280x1024. I don't know if it was originally designed for 1024x768, but if it was... they did a poor job.
I was a loyal TGF addict untill I just started using mmf2- it really didn't take long to get used to everything. If TGFers force themselves to use it for about a week I recon they won't be able to go back.
It's really well suited to widescreen, because you can have all the side windows and still have a decent width on the frame editor.
Most grid-based games would benefit from a solid well constructed level editor though, for a number of reasons. One of which include a minimum number of frames in your game, and if it's well designed, levels will be easier to make anyway.
I'm using TGF because I can't afford anything else.
Which is why I'm entering this competition (i.e. please let me win, it'll mean you'll get to play some brilliant games for a change )