Yes, and you forget that other platforms don't have Tortoise, and looking at a diff of a single file would be a lot more practical when it's open in the IDE...
Well first of all there is not only Tortoise (which I don't like at all, btw) and for other platforms plenty of different really good tools are available, too. It should be clear that we will never reach the richness of an application created only for version control. I use SmartSVN which runs on all platforms and I am very happy with it. I also see that many of the features are rather complex and have been developed in decades by the (SmartSVN) team. So I think we should not try to re-invent the wheel because we can only loose.
That doesn't mean we don't want to get a plugin. For me, what I am missing most is basic functionality like the virtualisation of a VCS state in the project tree and surely the basic functions check-in/out ...
Then as a second requirement I would like to have an extensible plugin, meaning that I can configure the most important commands so these match my needs. For Diff, there is the cbDiff plugin which is really good, in fact.
All in all I think the approach to integfreate VCS in the FileManager plugin would be my favourite and dmoore has started it already some time ago. That doesn't mean I don't like Git/SVN/...only plugins but the more we get of these trying to pump in all features and failing the more I believe we should make it really simple in the first place but considering the most important features from the beginning.