Hi there,
I graduated in 2004 with a degree in communications... worked in software development... and then in January decided to pursue dentistry. Since I needed to keep working, I decided to take the classes course by course at a small 4 year university (I live in New York City). I started w/ General Bio I and General Chem I and got A's in both, mostly attributed to the amount of time I was able to spend studying for each and my small class size. (The only science course I took in college was an astronomy course!)
I'm going to do the rest of the pre-reqs over the next year and apply next summer for the 2008 cycle. I looked into post-bacc programs at Columbia & Hunter College but I thought the courseload would be too much for me while working. I don't think there's any disadvantage to taking the classes at a university without a formal program. I also had many students in my class doing the same thing I was, and the pre-med advisor has been more than helpful to me.
Let me know if you have any questions. Good luck!