Definitely worth buying, but you need to shed the WOW mindset of "rush to max level", cause getting to 50 is going to take you 5 days PLAYED on average. That's also not what this game is about, clearly. Not yet anyway. The focus lies heavily on the leveling content and the class quests and those are really nice to be honest.
The PvE content is fun, and as usual PvPers will cry about PvP but the fact of the matter is that for a game released, the PvP content available is relatively balanced, though I hear the gear is unforgiving for freshly dinged 50s. However, it's not really complex to get gear so I don't think this should stop anyone. The instances (flashpoints) are diverse and really awesome TBH. Up to level 35 they're all easily 2mannable with your companions, and probably after that as well.
The hard mode flashpoints are hardmode (max level), in the sense that you can't really fail else you simply will die, but once you get the mechanics and tactics down and you know wtf you're doing and have a minimum of gear, they're not that hard really. Anyway, it's definitely worth buying and at least playing that free month, you can't really not like it unless you have a thing against RP/MMOs to begin with.