Is Feebas Worth Catching?
Well, in what sense do you mean? For battling? Filling the Dex?
Battling:
A lot of people compare Milotic to Gyrados because of the pre-evolutions being similar (a useless, ugly fish). But really, they are very different when they evolve; totally opposed stats, actually: Gyrados is physical and is more offensive, while Milotic is special and is more defensive. Other than their matched types, there's no reason that you can't have both on your team. Especially if we're just talking about using it for the main game.
Dex Number:
If you find it irritating to catch and evolve, I'm sure you can find a Feebas pretty easy on GTS. As other people have said, you can buy dry poffins in platinum to evolve Feebas.
But really, I like the challenge of finding/catching feebas. However, I don't bother catching Feebas in Platinum anymore because the spots change every 24 hours. :/ In emerald, it doesn't change overnight, it depends on the "trendy saying" being changed (right?).
Anyway, doesn't matter. Just catch what you like! I like both of them.