I use both of these programs. I really like them. Peak is fairly easy to understand. Deck has a slight learning curve --- and your hardware is essential (ie: audio card). You can get away with only using the built-in sound input, but the process would be very slow for a multitrack project. While USB is a cheap, easy way to go, it's been plagued with problems. I've heard good things about MOTU and M-Audio cards/boxes (I have a Delta 1010). You'll need to do some research and match the box to your needs.
I won't lie, there are some bugs in both of these programs, but if you're just starting, you won't find them for a while (until you get to the more advanced stuff). None of the bugs keep you from doing anything, but make some stuff difficult.
I'd be happy to answer any questions you have (you can PM me). Or, join the Bias Peak/Deck mailing list (once you register your programs). There's also a forum that's just been started and needs posts badly to make it stick around.