I'm really enjoying the voice acting. But I wouldn't want to see it in every MMO. It suits a Bioware MMO because it is their speciality and it continues the legacy of good voice acting in their other games such as Mass Effect, Dragon Age etc.
In the main the voice acting in Swtor is very good, though it can be a bit patchy, especially with some of the bit part actors, but thats perhaps to be expected. After all there's a huge amount of lines recorded.
So far I've played male Inquisitor, male Imperial Agent and female Bounty Hunter and they are all voiced acted very well, especially the male IA (I guess it's because I'm a Brit and I love the sarcastic and cynical tone that Bertie Carvel brings to the role). I did also start a male Jedi Consular and rapidly lost interest because the actor's lines were so dull and the storyline didn't engage. So I can understand both side of the argument here. It does very much depend if you can make a connection with the voice acting for your chosen class and this will be a matter of taste and can break the immersion factor for some.
Those who spacebar through everything on their first run through are missing out. Even on repeat play throughs different classes and genders get different reactions from many quests, plus theres the issue of how your companion will react to your choices depending on what you say and do. Yes there's some filler and not all of it is worth listening to multiple times, but much of it is.
I'm actually quite surprised by the depth of content they've managed with the voice acting. Yes, you could have even more depth with text. But lets be honest, in many games much of the text in quest descriptions is pure waffle and tedious drivel. I think one of the advantages of having an actor need to say the lines is it weeds out some of the bombast and pomposity that often permeates quest text in many games (though here and there it still pops up in the voice acting).
Ultimately, this is one of those things that is bound to divide opinion, it's a matter of taste.