In fact the Airport Oberoi is under construction and should open late 2010 ( Indian time ). 2 weeks ago it looked more like late 2011 ( European time ). Otherwise you have nothing at BLR airport.
I normally arrange for a hotel driver to pick me up. Immigration is easy, quick and really friendly ( not like the USA ). Baggage handling at BLR is world record in speed. I am normally among the first ones out, directly through PP control and the 1st bags arrive when you go down the stairs. It takes about 30 minutes to the downtown hotels at this time of the day. Don't take the "black" taxi's offering their services outside of the terminal!
On your way back, do the same thing.
The lounge which *A uses is not really fantastic, really crowded after midnight ( 3 widebodies leaving within 1 hour ).
A better option is the Kingfisher sports bar