Gearing

I'm currently riding a crappy street/hybrid thing running single speed on 44/16. According to the gear calc that's 74,3 gear inches. If I move to a nice fixed gear running 48/17 (that's 76.2 gear inches), is the difference going to be noticeable? I'm guessing I'll benefit from a lighter bike, less traction etc.
Currently the ratio feels about right, in that my speed is good and I don't need to get out of the saddle too much, which is how I like ti ride.

It will be noticeable when you first change because of you being used to riding 44/16. As Chris said, even a difference of 1gi is noticeable when you first change, but you'll quickly get used to it.