My first place was on 31st street and 24th ave ( i lucked up, with the beergarden and the park so close)... i always felt that the north/south border was Astoria Blvd itself. Not that its even distance wise, just because mentally walking over the highway always felt like you in a different area; either direction. Plus the ditmars area (where I am now) does feel very different than Broadway or 30th Ave.
31st Ave is lovely though. That was our #1 area to move to but there was nothing we liked available at the time.
I will say being in the 40's is also a very different Astoria experience. Walking down Steinway to the R in the morning was not fun. (garbage).