My two pence worth. I love DS9 and I love Babylon 5, and I think I'd pretty much conccur with what most people have said, chances are if you liked one you'll like the other.
The first season is the show at its weakest, but as has been stressed, the groundwork is laid for some fantastic twists and turns, and even if you don't think much of S1 after seeing it, I guarantee by seasons 2 and 3 you'll be looking back and realising what you thought was throwaway stuff wasn't that at all.