I ran the new version of Molten Core the other day. It was a lot of fun and rather nostalgic.
It was pretty funny how similar it was to MC back in the day. Herding 40 people, with about 20 being competent and carrying the rest. Wiping on trash. Pulling trash and bosses at the same time. Begging the mages to remove curses.
Our first wipe happened because we pulled 2 corehound packs together, and the got caught in an eternal resurrection cycle. Otherwise it wasn't too bad, I don't think there was any more outright wipes, though there were a lot of deaths.
The bosses were fairly easy, probably easier than the trash. It was good to see Ragnaros again. Plus you get a helm and a mount.
All in all, the new Molten Core was a fun experience. It's worth gettting to i615 and trying it out before Blizzard removes it.