That was one of the fears I had about getting a PhD. Waking up one morning and realizing that I had devoted 6 years to learning two dead languages and writing about farming in the 2nd century BC and that I just didn't want to do it anymore. I'm not over the moon with the work I do, but it'll make sure I always have a job - and one that pays reasonably well.
This was a bit of a problem for me. I had co-chairs on my doctoral committee, both of whom were actually decent and certainly were/are stars in the anthropology firmament. They cashed in their fame while I was away doing fieldwork overseas, each going to a school on one or the other of the coasts, leaving me to make do in the midwest. Neither one of them was around to really help with the final phases of dissertation writing ("don't send me chapters, I just want to see it when it's done") and didn't pull strings on the job market for a generation of us grad students. But honestly the real limiting factors were a) I didn't go back to the field to collect the data I would have needed to turn my dissertation into a book and b) I limited my job search to the commutable distance around my wife's employment. All of this would might have been overcome by a bit more drive, ruthlessness, etc. I did land several visiting assistantships and got very good teaching evaluations, which is of course no help at all in most tenure track job hunts. I'm doing interesting soft-money funded research at a decent university with people I like and respect now, but the money's only okay and soft money positions are fraught with shall we say tension. On the other hand, I did hear of an English lit PhD in the area who's pulling down 6 figures editing self-published vanity autobiographies and family histories for wealthy dilettanti.
That may be the norm at Berkeley, but I'm not sure it would apply at places with a more reasonable cost of living. Here at UNC, I think it's common for grad students to subsist only on their TA stipend.
Advisor advice: Things to consider that I think we can all agree on: a. prestige of advisor b. willingness to go to bat for students c. ability to go to bat for students (ie: job placement!!) d. personality/ easy to get along with/ compatible style of researching There are other things as well. Jasen: More than likely you can take a class or 2 before you actually start the MA program officially. This would give you a jump on the requirements, alleviate pressure down the line and jump-start your brain.