Very exciting with Cataclysm to have new 5 man dungeons. I love running with just a few friends, especially when none of us have seen the content before. It will be awesome.
Apparently there will be 8 new 5-man dungeons including new versions of Deadmines and Shadowfang Keep. I think it is a brilliant idea. It always seems shameful when these wonderful little instances disappear as new expansions arrive. Perhaps I'm a nostalgic sap when it comes to the older zones (or perhaps because I'm tree hehe..sorry couldn't resist) but I love going into the old zones.
5man dungeons are where it all started and I would love to see more of the players that are leveling toons get the opportunity to play them at their level. Most of us just get ran through by a high level guildie. Hmm perhaps that could be a project for your guild. Level up very slowly together and run those old 5mans. I'm sure the prisoners at the stockades are waiting for you. Ewww creepy hehehe.