I debated on the spoiler tags. But at this point, I'm just guessing. So here it goes...
1) What the hell...only 4 out of the 5 "missing" Cylons showed up. Hmmm....does that mean Baltar or Kara is #5 (or even Hendrix, no human can play a guitar THAT well...LOL)
2)Speaking of such, here's the particulars on that version of "Along The Watchtower"
http://www.bearmccreary.com/html/blog/blogmain.htm
3)I think Moore said earlier this season that the revelation of the "final 5" would make people "rethink what it means to be Cylon." Clearly for many of the reasons people are already bringing up, that's the case. The "Final 5" are definitely something vastly different from the other "skinjobs." How different of course remains to be seen, but even the other skinjobs don't know who/what the "final 5" are. Tigh's presence means that some "skinjobs" are as old (or older?) than the original mechanical Cylons. Or at the very least that some sort of Cylon "presence" has been around predating the first Cylon War.
Of course, this is all operating under the assumption that the characters are correct in believing themselves Cylons. Certainly it's the logical conclusion for them to jump to within the confines of their own in-universe experiences. But as the viewers we know this show likes to play with people's expectations, so there may very well be another explanation that we have yet to see. Or maybe it's a combination of both. Either way they're definitely "different."
4)....and finally....
I've been wondering from almost the beginning if the whole "Earth as the lost colony" isn't a sham, and in actuality the colonies were founded by Earth in the distant past, but for some reason lost the historical record/whatever. Basically that the "Lords of Kobol" were commanders of colony missions from Earth or the like. It'd explain most of the "parallel development" that we've seen better than "colonists from the colonies came to Earth in the distant past, but we forgot everything/lost the technology, then redeveloped most of it again."
I find it interesting that the Colonies have this history that stretches for millenia (and apparently had interstellar travel capabilities for that entire span of time), but no one's made any mention of where the "colonists" originally came from. Who were the ones doing the "colonization" in the first place? How does a society that has FTL/Interstellar travel capability for millenia not have a complete historical record of this "lost colony?" Clearly something has happened in the intervening millenia to mar their knowledge of history. They might arrive at Earth to find a lifeless, used-up (natural resource wise) husk of a planet.