Level 44 currently on my main character, a Sith Assassin.
I also have a level 20 Sith Marauder and 18 Imperial Operative.
Clearly I won't be able to give you an endgame perspective as I'm not quite there yet (level 50), but I've found the levelling process enjoyable with the heavy emphasis on the storyline.
That said, I went with a PvP server choice because I've always done so, and always enjoyed world/open PvP on a large scale, rather than arena/warzone play. Unfortunately, because of the 2:1 ratio of Empire to Republic players (on my server; Hex Droid) and the rewards being provided by winning warzones, there is very little of this and it's something I'm having to be patient with. They've stated already that they hope to remedy this in what they're calling the 'New Year PvP Update', which implies it'll be arriving around the start of the year, where there will be incentives for open PvP.
There are also a couple of classes that are being deemed as "overpowered", as you expect from any MMO launch that incorporates PvP, but there really do seem to be issues with a particular Sith Operative if talented specifically and buffed, to the point where their rotations drops tanks without allowing them time to break out of it. As I said, I'm not at level 50 so I can't judge personally, but there is a lot of barking about it on the forum.
Crafting needs looking at, as there are a couple of fields (Cybertech and Biochem) that are worth picking up, whereas everything else is practically worthless since endgame armour is so easy to come by if you're willing to invest a bit of time in warzones.
Anyway, I'm enjoying it like I said. I'll post another update in a week or so when I've experienced level 50 for a bit.