I'm brandy-new here, but saw this thread and felt the need to post.
I don't have any regrets gear-wise thus far. I learned on an old Pentax SLR that my Dad had from his time in Vietnam. My first camera was a Nikon N6006 SLR that was a high school graduation present. That camera served me well as I got into B&W, worked with the yearbook in college, and generally became "that guy" who always had the camera at events. The best man at our wedding gave us a gift that allowed me to get into the digital age with a D70s. At the time, I had to go with the 18-70 f/3.5-5.5 kit lens. It's Nikon glass, but not much better than the 35-55mm that I had on the N6006. Still, lots of practice and lots of learning from others allowed me to get some good shots. I've had my Dad's old Vivitar flash unit, too, which has served me well.
I was recently asked to help photograph a friend's wedding, and so decided to do a serious upgrade. Later this week, I will become owner of a D700, a 24mm f/2.8, a 50mm f/1.4, an 85mm f/1.8, and an SB-900 (yes, all Nikon). After a lot of research, I think that this will get me to a good spot while I work on saving for the next upgrade in glass.
Given the cash that I just dropped on that gear, my only perceptible regret is that I didn't invest in better lenses earlier. The expense usually caused me to shy away, as I was getting "good enough" from what I had. After using a few of my Dad's lenses over the past few years (he shoots a D70 with high-end Nikkors), I wish I had bought a few along the way, so that I'd only be looking at the body and maybe lighting upgrade now.
This gets my collection started, though, and I can't see any serious regrets in the future. Who knows what Thursday will bring, though....
jonathan