Recently I participated in the TERA Open Beta and had a pretty good time running through the fetch quests and destroying everything with my Archer. Here's a video highlighting some of the highs and lows I experienced through the beta.
On a more serious note I actually did have a lot of fun with the beta. The questing sucks if you can't bother to read the text behind the quests but the combat more than makes up for it. Your class choice does affect the amount of fun you have in the game which all boils down to personal preference. In my opinion it's worth buying but I'm not too sure on paying for an ongoing subscription model. We'll see how the content fares later on, apparently the game gets loads better once you get up to level 20.