It's nice to see other people talking about Doctor Who in a positive light around here.
I've never been a Who fan. It's not that I don't like it, it's just that I never see it when it's on, and I feel like I don't know enough to just jump into it.
And isn't this Doctor supposed to be the last?
Nope. Time Lords can regenerate a total of twelve times (normally), and Matt Smith is the eleventh Doctor, meaning there will most likely be two more after him. Not sure what'll happen after that...
I couldn't say whether or not he's the last, but let's just say that I both hope and doubt it.
As for the continuity of Who, you don't really need to watch the (really, really long) old series of who. All you need to do to get caught up is watch all of New Who (and maybe some Torchwood), which is roughly comparable in length with either Heroes or Lost.
It's not even that long. There have been four series of New Who so far, and each one is only 13 episodes long, plus a Christmas Special. Then there are the four 2009 "special" episodes bridging the gap between those series and the latest one, so it's a total of 60 episodes. Or 63 as of the latest one (Victory of the Daleks).