Other mods may have cloned parts of it, but I liked Eloraam's overall style to her mod. I felt that ComputerCraft computers were more flexible, but there was something about having a "real" computer to play with which appealed to me, especially from having experience with 6502 chips and assembly. I'd also enjoy seeing what she had in mind for blutricity, because it had a lot of potential. I don't really think she's coming back, though, especially after a clone has become so commonly used, even here on FTB.
Pahimar has been working for a long time on that new system for transmutation in EE, so that should be interesting. I was just wishing that I could transmute some things I didn't need the other day.
SpaceToad's return has resulted in new features for BuildCraft already, so it's exciting to think what he'll have in store in the near future, and hopefully till 1.8 and beyond. I'm going to grab the alpha version to mess around with here soon.
Thaumcraft seems to have cemented itself down with some pretty great additions, but I don't think he'll ever stop redoing it until he's perfected the research system. That might mean another total overhaul, and if I had to bet, I'd say that would probably be sometime around 1.8 as well. But that's fine, it's always interesting to see how he reimagines the mod. He's another of those modders who just has a particular style which could never be cloned.
I'm sure there's others I could think of, but that's enough for now!