I like DD-X personally. Easy to use, great results.

The only complaint I've heard about DD-X is that it is a bit more expensive than the others. Not enough extra to keep me from using it and there are ways to streatch it.

Whatever developer you choose, my advice is to read and follow the directions, then get good following the instructions. If you do that you will get good usable results every time. One of best things about getting good at following the directions is that when you decide to use a different film you will be able to get good results on the first try.