One way to speed it up (although if it only takes a minute to replicate anyway you probably won't see a difference) is to host the GC on all domain controllers - MS say only one DC should be host the GC for various reasons, but if you have more than one then as long as all DC's have the GC local to it then there won't be any problems - unless you have Exchange installed on a DC - if you do, then this should not host the GC.

This will reduce replication timings a little bit, but due to the way replication works (Inf master talking to the PDC etc) one miniute is considered pretty good.

You can change it to replicate over IP instead of RPC in the AD Sites and Services too - this will help with speed.

All of the above normally only really applies if you have drastic replication issues though (10 minutes or so)..