Hey, I'm goin to Girton to study MML- I may not have done the trip every day for a term (yet!), but i do have some thoughts on it!
First of all, all things considered...its really not that far! Just cuz its cambridge ppl seem to think that a 15 minute cycle ride from lectures is enormous, simply because of the proximity of the majority of colleges. But i guarantee that if you look at any other large(ish) city (even Belfast!), nearly all student's halls are an average 10/15 mins from the city centre! And some are much further! I have a few friends in Edinburgh who have to travel half an hour into town every day!
Secondly, i think it can be nice to feel that you're "coming home" every day from the academic pressure cooker that is Cambrige city centre! ...Not to mention the increased fitness from all the cycling! lol.
Finally, the distance gives Girton so many advantages that are overlooked with all the emphasis being on the negative aspects! The grounds are unique among Cambridge colleges, all the sports facilities (ok, ok, except the boat house!) are on site, it allows Girtonians to live on (relatively spacious)corridors instead of cramped staircases...and we too have a duck pond! (yah boo sucks Emma! lol)
So, i hope that helps!