Nothing really beats an excellent prime, but honestly you can't go wrong with the 50-200mm. I bought it on special at a local camera chain going out of business, and hadn't taken it out for a few months... Took it out for a field test today, and I have to say I'm very impressed by my copy. Corners are definitely a bit soft, but there's not much you can do for the price this lens goes for. Mine does NOT have quickshift, plastic mount.
Here's a rather large album I just took today. The Photo is a full crop slightly off centre, still with near full sharpness.
Click the pic to get to the full album.