09 Meta 5/6's tended to crack at seat tube / top tube weld
08/09 Meta 5/6's also cracked around shock mountings
09 Super 4's have suffered cracked chainstays
Not heard of that many problems on the Mini DH's
(some Furious's seem to have had bad alignment and issues with piggy back shocks hitting the frame)
2010 stuff seems much better, far superior build quality from what Ive seen (I have an 08 Meta and an 09 Titanium Commie HT and a large bunch of us over at the commie owners club ride together so Ive seen and heard many stories and experiences of cracks and replacements)
2009 models that break now being replaced by 2010 frames generally
Warranty procedure through Madison now seems much smoother (send photos of cracked frame, serial number etc, no need to ssend of damaged frame for inspection) turnaround can be low as couple of weeks but some shops (mainly larger chains) still seem to be messing people around and insisting on returning the frames and delaying things
Plenty of info and threads with peoples experiences on http://www.commencalownersclub.com
post up there and you will get no end of advise from other owners
You might like to wait for the new 2011 Supreme 8 though – due in country later this year, looks mint