Yes, Flann O'brien's is indeed the pub in question. Was in Boston a couple weeks ago, and had a couple (ok - 3) pints there. I'm from Detroit, and would have known what to make of the place, were it here in MI, but that was a bit of an odd neighborhood. Couldn't quite get a handle on it. It was a cool enough pub, and would probably go back there again.
i used to live almost right across the street from flan obrien's, more up across from the post office/high rise apartments. this was about 4 years ago now, but at the time, it was a great little irish pub, owned by actual irishmen that you could go to relax and have a pint and some GREAT food for lunch or dinner. and then at night have it pick up a bit and have a few too many pints and and have a good time with friends.
you're right though, it definately is in not the greatest neighborhood. years ago it was really a ghetto, but has been on the way up over the past few years. nowadays it's becoming more of a college kids area and gentrification is in full effect. =\
if you're ever in the area again, if you walk down the side street that flan's is on, you'll come across another excellent little irish pub called the squealing pig. another great irish-owned (i stress this because too many "irish" bars in boston are no longer irish owned, they just cash in on the boston/irish stereotype) with EXCELLENT food and great entertainment (check out thursday nights if you can).
Hmmm, I had guessed it as a neighborhood in decline, not on the rise. There were a couple boistrous drunks in there (and at least a couple users, I suspect), passed out or sleeping one off, as well as two guys sharing a stall in the men's room. I did take a walk down that side street (unfortunately not far enough to discover the Squealing Pig), and it's a cool street. Lotsa good old architecture in need of some renovation.
One of my favorite ways to travel is by use of local pub guides, though we didn't plan enough in advance this time - just happened across this place by accident. Also visited the Green Dragon, which is not the kind of place I'd normally be drawn into, but it was a Sat afternoon & it offered a nice enough refuge from some very heavy rain before a walk into the north end for a fantastic espresso (& grappa). Place was all but empty & we chatted up the (real) Irish bartender. Also went into a pretty decent pub in Cambridge, but I can't remember the name. Boston's a cool city & I hope to visit again.