I'd say from experience that significantly less effort is spent transitioning to git than is spent worrying about and complaining about git before actually trying out the switch.
It took me a few hours to learn enough in git to replicate my experience in svn; sure, it takes longer than that to learn some of the other features, but the only time that is actually lost is the time spent relearning what one already knows.
If you're just replicating Subversion, why use Git at all?
(I'm not being flippant -- I hear this from people all the time, and it really makes no sense to me. If you're just going to set up a single central repository, why wouldn't you use the proven, capable tool for that workflow? Git is rather poorly documented, and works with only a tiny fraction of the professional tools that support SVN.)
I didn't say I was only replicating--I said that it took me a few hours to be able to replicate SVN. The reason you switch isn't to replicate SVN, its to take advantage of the other features available, like local commits (see http://news.ycombinator.com/item?id=374413 ).
My point is that the only time you lose is the time you spend relearning what you can already do with SVN: all time spent learning new things isn't lost time at all.
It seems to me that Git's ecosystem is rather more developed than Subversion's, despite its younger age. I haven't seen any hosting service for Subversion repositories that approaches GitHub (and even `gitweb` is pretty nice actually) and the amount of stuff in e.g. http://git.or.cz/gitwiki/InterfacesFrontendsAndTools is pretty huge compared to what I've seen for SVN.
When it comes to documentation, not only is the reference manual excellent in the usual way of Unix reference manuals, but I also know of six tutorial Git books, several of which are free online: the Git User's Manual, the Git Community Book, Git Magic, Pragmatic Version Control Using Git, Pro Git, and Git Internals.
As I said in another comment (now deleted), I'm using Subversion on a project for the first time in years, and I constantly find myself wishing the project was using Git.