WAY BACK IN THE DAY ... when I was just starting playing gigs, there was a guy who played piano and every song was in 'C' ... after a while all the songs started to sound the same ... Now with the 'Transpose' key it is easier to play all songs in the same key but vary the keys people are hearing ...
As for me, I like playing songs in the original key - unless of course it doesn't fit my vocal range (which is not that great) -
I really like playing in the keys of F,G,Eb,Bb, perhaps because so many of the 'Standards' are written in those keys, and those keys often fit my vocal range ...

Ian, when I read that you enjoy playing in A and E I immediately thought 'he must have played with a lot of guitar players' ... it's kind of funny to me that I don't mind playing in 3 or 4 flats, but don't like playing in 3 or 4 sharps ...