In the blogs I am reading, nobody mentions Rift any more. The last thing I heard was several bloggers complaining that as they had played the game less intensively than others, they got "left behind" in underpopulated zones, with everybody else playing at the level cap. The spontaneous multi-player experience of rift invasions was one of the major selling points of Rift in the early days. But it seems you had to *be* there in the early days, because by now you missed it.
So when Melmoth writes about Star Wars: The Old Republic: "I honestly can’t remember an MMO where getting in from the very beginning has made any difference to my experience", I don't agree. There have been a lot of MMOs where getting in from the very beginning has made a huge difference to my experience. Even in World of Warcraft I have fond memories of dungeon groups in the early days, a part of the game which then completely disappeared as people outleveled these zones, until the Dungeon Finder brought low-level dungeon groups back in a diminished form.
But then Melmoth sees the game as "SW:TOR seems to all intents and purposes a traditional single player Bioware RPG but with the option to bring friends along." And if you want to play a MMO in single-player mode, waiting for the first wave of players having rushed past is probably a good idea. The classic Star Wars line of "you are our only hope", even with voice-over, isn't going to make much sense if you're among 37 other jedi chasing the same quest mobs. In single-player mode other players in a MMORPG are just a distraction, or worse an obstacle.
So in the end whether it is a good idea to start a MMORPG on day one or rather to wait a couple of months is a function of the single-playerness of the game. I'm still hoping that SWTOR has enough things to do in multi-player game modes to make starting early worth it. And if there is really no sensible group activities in the game, I'm not going to play it very long anyway.