I have just been listening to
a recording of a recent Belle & Sebastian gig at the Hollywood Bowl, backed by the Los Angeles Philharmonic. The recording came out very well (with the exception of the usual chattering idiots you get at gigs, though they're not too obstrusive), and it sounds like it was an impressive show; the orchestral arrangements work really well, and some of the songs sound better than the regular versions without an orchestra.
I was at the show; seeing La Pastie and Your Cover's Blown with the extra arrangments was amazing. By far the best B&S show I've been to.
As for the chattering idiots, you must be aware of the nature of the Hollywood bowl: it is a casual, outdoor venue where people bring their families, food and wine and picnic during the shows. It's rude, sure, but not entirely unexpected considering the inevitable "could you pass the wine"s and "quiet down, junior"s that would occur.