I've looked into them. I do like the super high frame rates. 18fps for most of them? That is ridiculous. The biggest problem is they do not have an optical view finder. Makes them great for shooting scenery and such. Action? Not nearly as good. I'll stick with the DSLR.
mine goes up to 10fps - i haven't heard of 18 yet, and although that would be so fast it'd be a pain in the ass deleting all the shit you didn't need it wouldn't surprise me to see someone has it.
with no mirror looking thru the lens optical vfs aren't possible with this tech. they use electronic view finders. i made sure to spring for the nex7 with the evf built in. no, its not an optical vf - but it does very well in snow. olympus em5 also has evf.
it is worth the weight savings alone to give these cameras a serious look, imo, even if you don't end up seeing one that is right for you, yet.