This is a pure opinion piece and a little trip down semantics lane.
I prefer to think of the current version of Revit according to the build, not with service pack numbers. I realize that just knowing which you are using by either method works technically.
So what is a build, if you don't know already? Software is compiled from a version only software engineers can use. Compiled is another techy way to say it is has been prepared for use by your computer.
Until recently all releases of Revit referred to a build number formatted YYYYMMDD_TIME (24hr clock), for example the current Revit Architecture build is 20071109_2345 and also referred to as Service Pack 3. The software is compiled many times, weekly if not even daily or hourly at times for internal testing by various team members. They use this build value to differentiate between versions constantly. It seems only natural to use the same method to speak about the software when it is compiled and released to the public.
While this habit might be a little unfriendly to the lay person it has been the way and consistently so. Now we are also referring to service packs. The root of my complaint is the half-hearted, skin deep application of it. I say this because the only place the service pack reference occurs is on the web site and in documentation available there. After that the build number reappears, even in the release documentation detailing what the build addresses.
So I say (from my bully pulpit) bring back the builds and can the service pack. It is useless, redundant and even confusing to use both.