There are several polls and posts flying around the SWTOR forums about competitive arenas.
I personally don't want them in the game. I don't want them not because of the blizzard did a shit job implementing in WoW but because I don't think that Bioware will be able to do much more than blizzard. Don't get me wrong, Bioware > Blizzard, but a game has to be built around arenas to support competitive arena play.
In order for a game to fully support arena-type gameplay you need to build the game around arenas. Which means that you need to balance things out around small groups; progression focused pve has to be cut from the game; and the number of abilities each character has needs to be drastically reduced.
I'd rather see rated warzones, engaging and meaningful world pvp than arenas. It's not about the gear grind, because that's what theme park MMOs are about, it's about the rollercoaster ride of buffs and nerfs which bleed over to other parts of the game where they're not needed.
I enjoyed them in WoW, but i enjoyed battlegrounds, rated battlegrounds and world pvp a lot more than i enjoyed arenas. The only form of arena play that i would support, would be if they just keep them as a spectator mini-game. Think of them as glorified duels that happen in different maps that people can watch and gamble on. Just as a little something to pass the time along with (hopefully) pazaak and swoop racing.