I haven't hit elder game material yet, but I can tell you two things:
1) There is definitely a substantial RP element here. I transferred from Jedi Covenant only a couple months ago, and I haven't done any RPing myself, but witnessed quite a bit of it. Even in general chat, when the population isn't too high, people will RP; no one really minds, most only find it entertaining
2) This is just a nice server in general. I remember running into some not-so-great players on other servers, whether in group ops or otherwise, but I haven't had a problem yet here. I've done a dozen or so flashpoints, helped out/been helped out with planet-side quests, and the like, so I've been teamed up with a bunch of people, and I haven't disliked a single one. People either want to help and get along, or are completely indifferent; it's just a mature server.
Granted, this is all imp side that I know; I haven't made a pub toon yet (though I plan on doing so soon). Totally up to you whether you spend that $15-18 or so to transfer; I did, and I don't regret it at all.