Oh man, I should show you the tiny start I made to my own "deathtrap dungeon". The entrance looks kind of cool and one room is complete, but moving an arse load of lava there made it take forever for what was a tiny result.|
Creative mode will be the key. If you like / care about leaderboards and achievements though, I'd recommend you do it in a new seed and keep eggmilf a pure map. I've actually done new generations on a couple of 1.7 seeds I like and explored them so I can use them with the new abilities in 1.8 (but not the terrain generation...)
The race to find awesome seeds again will be fun. Who knows, eggmilf may turn out to be terrific in both versions. I should post the seed number for my other favorite seed. I think the words were "Covenant, Unbeliever" (sans quotes but with comma) because initially thought to try and make Revelstone from the Thomas Covenant novels.
It has the best snow / forest / desert-plains balance I've ever seen, with almost the whole north winter and terrain that generally feels very natural. Downside is only a small (but serviceable) area for islands. Just about the only significant water area is a frozen lake in the north.