Do it!
I just got my first blackpowder gun a few weeks ago. I opted for a Pietta 1858 New Army.
So far, I've been tickled with it. It's fun as heck to shoot, though it does take a while to load. I'm considering ordering an extra cylinder for it. Only thing I have mixed opinions on is the barrel length. On the one hand, I love the look and feel of the 8 inch barrel. However, I'm looking into getting into cowboy action shooting, and that's a lot of gun coming out of the holster.
Since you asked about cleaning it like other guns, I'll tell you my thoughts...Everyone and their brother is going to tell you to use water. Personally, I don't much feel like it.
I use modern solvents alongside Hoppes Blackpowder Solvent. If you're interested, you can check out my thread in the BP section at the URL below. It works for me.
http://www.thehighroad.org/showthread.php?t=540104
I have to agree with what the others said, BP is addicting. It's fun as heck to touch off that first chamber and watch every head on the range snap around to go "What the heck was that!?" It's enough fun that I just bought another gun, an 1851 Confederate Navy Sheriff.
It's a 5 inch barrel, so I'm thinking that'll be a bit better outta my holster in Cowboy Action stuff.
I bought my 1858 with the starter kit. I'd suggest that you do the same, as it's a decent value. You get a nipple wrench, 30 wads, 30 balls, a powder measure and flask and some thingum called a capper that I can't for the life of me figure out how to use.
Last tidbit! Cabelas has a free shipping offer valid through midnight tomorrow. Not to put a time rush on you, but it's like 18 dollars to ship normally. They're usually running some manner of shipping special though, so watch for it. It was 5 dollar flat rate when I bought both of mine. Wish I'd waited on buying the 1851, because 3 days after I purchased, this free shipping thing kicked in.
I say buy, shoot and enjoy. There's a TON of resources on this forum that tell you all you'd want to know and more about the New Army.
Hope that helps!
Packman