Like you do, I see the PhD (at least) like a full time job, so I come into the office every weekday. I think it really depends what works for you - I cannot really work well at home, as it is too much associated with relaxation and "things away from PhD", but I know several people who work from home a lot. I think it is good to go into the office as you develop a good work ethic and routine, you are available for other people (your sup, co-workers, friends) and other people are directly reachable for yourself, and sometimes in that way, solutions to problems are found quickly (no emails, waits etc required). Plus, there is an element of seeing and being seen, and it is important that other people in your department know that you exist (and maybe know what you do). You say your office is busy, so yes, I can see that maybe you might work better at home... What's about listening to music whilst you work, in order to blend out the distracting noises from others? I do not work with music myself, but know that fellow students find it useful. Hope that helps?!