It's fun, buying new stuff and seeing what you can do with it. But in reality, I haven't bought any real camera equipment in over a year (aside from memory cards).

My focus (no pun intended) has always been aircraft photography, so even though I have purchased a lot of equipment, many of the items were stepping stones - mistakes, in some cases - until I got the setup I wanted. I just kept them because they can be a pain to sell and do come in useful some times.

I bought a 20D and it came with the 18-55 EFS lens, and you can't hardly give that away, let alone sell it. Plus, it's a nice, cheap lens for shooting work gatherings and stuff, where image quality is not that important.

After that I tried to get a cheap air show lens, and bought a Tamron 28-300 lens. After a few shows, I wasn't thrilled with the results, so I saved up and bought a Canon 28-300 IS lens, and after a few shows wasn't happy with its reach.

I finally got smart and did some research for the next one, and bought the Canon 100-400, and that's what I'm using to this day. I'd say it's on my 1D camera 99% of the time for what I do.

The only other lens I've bought is the Canon 50mm 1.8, which has to be the best lens deal out there, at under $100. I use it for those rare occasions when I'm shooting portraits, and it's great - very sharp, great DoF control, and small enough to easily carry around.

ditch that, its the worst purchase i ever made.. used it a hand full of times, it now sits in the corner of my office collecting dust..

learn to control light instead..