Supporting Vista Versions

I was reading about the 5 different versions of Vista earlier.
Lets forget MCE, Tablet and x64 for the moment.
What struck me was the difficulties that supporting 5 different versions would produce.
As you would expect, being a Shell/User MVP, I answer questions about issues people have with XP.
The problem is, I don’t always know what version they have, they don’t tell you in the initial post.
I have found myself typing long replies only to realise, it may be wrong, they might be using XP Home not XP Pro.
Vista with 5 versions will only exacerbate this. It’s going to be real fun trying to remember the features of each version and worse still, differing implementations of the same feature in a particular version.