Been doing my 10 mile one way commute for a little over a year. It's doesn't really seem easier but I'm alot faster than I was last year. If I deliberately try to take it easy I can get to work and home without feeling I did any work so I guess it did become easier.

I didn't do anything fancy. A few times a week I would try and "attack" every hill on my route. I'd try and go up the hill as fast as possible then kinda coast till I caught my breath and repeat that. Built in intervals I guess. Seemed to work good for me. I've been taking whey protein to supplement my harder ride days. It seems to help quite a bit with recovery.