I'm a little late to this thread, but I have used SlimDX for a year and I'm nearly but not quite finished translating my embryonic game to SharpDX (because I want to use XAML and a couple other reasons). I highly recommend both, and putting aside SharpDX's advantages (DX11.1, WinRT, XAML, some speed improvements), I would say that SlimDX is as close to managed DX as your going to get, it's equal to SharpDX, without considering those advantages that I mentioned.
I hope the point I'm making is that SlimDX is a closely mapped framework, equal to SharpDX. In that regard, SharpDX can't be recommended alone, without mention of SlimDX. And also I want to make the point that SharpDX will not minimize the migration steps over SlimDX, if that's what you're thinking. They are very similar, more similar than you think if you are of the opinion that you might fail in one and succeed in the other. If you can work it out in one, then you can work it out in the other, they are that much alike. So much alike that I wished they would rejoin as a team and work together on a unified package of frameworks. There is just too much overlap for them to be distinct projects IMO.