I'm biased towards Canon, but my real world experience with my 450D (XSi) has given me every reason to be. I have a small collection of lenses that allow for some flexibility while shooting (50mm - F/1.8 prime lens, EF-S 18-55mm f/3.5-5.6 kit lens, and a EF-S 55-250mm - F/4.0-5.6 zoom lens). Here's my opinion on a few things to think about in addition to choosing which body you'll be going with.
Knowledge - Learn how to even use your camera and kit lens to it's full capability. Here's my bible, although there are many great books/online tutorials that may be a bit more thorough than this. Bookmark this thread, and use it when you pick up your new camera. Also, browse these forums and get a feel for what people do and don't like about certain cameras/lenses/tripods/lighting/software.
http://photography-on-the.net/forum/showthread.php?t=414088Lighting - A solid lighting setup can sometimes trump the need/want for a new lens. The never ending question seems to be "what are the core lenses I need that will cover every shot I want to take". People get so hung up on buying new lenses, spending thousands and thousands of dollars when they've yet to even take the kit lens to it's full capabilities by supporting it with the proper lighting.
Editing Software - For as much as people concentrate on wanting the camera to do everything for them, that's just not realistic. Unedited photos from a solid camera/lens setup will be amazing, but not nearly as amazing as they can be after going through a few rounds of editing. What seems to be the most popular among my friends who are real serious Photogs is Adobe Photoshop Lightroom 3. I use the Aperture program through Apple, but it's a personal choice of ease of use and what gives you the best results. For the more serious Photog, Lightroom 3 can get you results like this (a good car buddy of mine, takes amazing photos, and has some great editing skills):


These are just a few of my opinions above, but I feel as though people get so hung up on what body to buy that they forget about everything else involved in taking great shots. To be 100% honest though, I have some friends with $15K-$20K setups that have no eye for composition. They have amazing shots none-the-less, but they just don't jump out at you like those with the ability to capture a particular moment.
Whichever camera you purchase, the kit lens should support you pretty well for just about any shot you'll take, but if you're taking enough photos you'll start feeling the need to pick up another lens that will further your ability to take some unique shots. Choosing a second or third lens is much more difficult than deciding on which body you want. I compared it to deciding on what wheels someone wants to buy for their car. lol Took MONTHS...

Good luck with your search!