The 35-105/3.5 constant-aperture lens is a real classic, and it's a good zoom range for event photography, where you're likely to be switching between single portraits and photographs of people in groups quickly and won't have time to change lenses, and if you're also using non-TTL auto flash, you'll get fairly consistent exposures. If you don't do that kind of photography, then sell it, and you can buy another nice FD lens. A lot of the top of the line FD lenses like the 50/1.2L or the 85/1.2L are real bargains, considering what they can do. I'm personally a fan of the 35/2.