I've used the Joby UltraFit Sling Strap for about 8 months now and I love it. http://joby.com/camera-straps/ultrafit-sling-strap-for-men/
I liked the idea of the Black Rapid strap, but was concerned with the scratching issue (from the carabiner) reported by a number of users. The UltraFit has a unique connector which makes it a non-issue. The quality of the strap and all the hardware is very high.
I really like the quick-adjustment on the strap. Makes it simple to move from being tucked close to the body and quick extension to eye-level. Plus you can lock it into a specific position with no effort.
For switching between body and lenses, I use the RRS B2-FAB-F flat-back clamp.http://reallyrightstuff.com/ProductDesc.aspx?code=B2-FAB-F&eq
Just thought I'd throw my (admittedly virtually-worthless) endorsement out there.
I'm actually surprised I never hear anyone mention it or see anyone else using it.