I have found them to be VERY good. Although I thought that the transports are skirmish ships, so if Mongoose is building anything new, the Vorlons could get a nifty Raid level (It's the Shadow fleet that has no Skirmish ships).
Anyhoo, a single Battle (At the Raid level) or War (at the Battle level) ship can cut down a ship every turn; well, at least that is what our local Vorlon player seems to be able to do. My first encounter was able to destroy a Minbari Tinashi with close blast doors in the very first shot of the game!
Also, to add some fuel to this maneuverable cheers/geers I find them to be as maneuverable, if not moreso than any other fleet. The 90 degree turns on those transports are plenty. The only thing they truly lack is port/starboard/aft guns, so they will take it in the teeth when encountering Vree or some other close-quarters fleet.
Finally, those fighters just rock. They have AAF and a 3 inch range beam! What is NOT to love about these things!
So, with great, long distance guns, very cool fighters, descent turn radii, this is one solid fleet.