One of the modern overhead carry-on baggage scrambles for space is the upper deck of an A380 in economy configuration.
In terms of "rear entry"....it is still regularly practised down here at CPT when boarding (but rarely deplaning) a wide body parked on one of the remote Eastern stands. In fact I always think its a rather lovely way to leave the Mother City on a fine evening (not so good I appreciate when its pissing down). Have also, in recent memory, used the rear steps boarding at DXB remote stands
Back in September 2011 I did a Scandi loop, LHR-GOT-ARN-CPH-LHR, just to fly the SAS Mad-Dogs (enjoying 2 x MD81's and 1 x MD87) before they were retired and was treated to a deplaning via the rear drop steps at ARN....the last time I ever enjoyed this unique feature, which like so many others noted, was a common experience the 1-11 heyday