Well a recent thread that shall not be named made me think of a good topic. Would you be comfortable shooting a major event such as a wedding with the camera equipment you own? If not, what things would you get/rent before you would be willing to do it?
I personally would not shoot a wedding or event with my D5000. I haven't had a chance to use many of the higher model Nikons, but I think they have some additional buttons for changing setting easier don't they? I would use my D5000 as a backup, but I would want the 17-50 F2.8 Sigma lens that I will be getting soon on it. I wouldn't use my 18-200 Nikon lens just because it is too slow even though the range is nice. I guess it depends on if we were outside or indoors.
So for me I would need a whole new body D90 or up, faster lens in the 70-200 range and a flash. I would think if you could get in on being a backup or assistant to someone shooting an event that it would be helpful for you. I also don't feel confident enough to be able to switch settings on my D5000 fast enough to be effective at a wedding. I think I would miss shots while I was fiddling with the settings menus.