Wilburforce - 9:34 am on Feb 25, 2013 (gmt 0)
I set up a (js-based device-detecting) forwarding service (mobile.mysite.com) in October last year.
There were some inconsistencies in the way the mobile version rendered (both between handsets, and between handset browsers). Also, I was reluctant to include the js outward link on all pages, so having trialled the forwarding version, I abandoned it in favour of adding more mobile-friendly css to all pages. I have retained the js version on my home page.
My own css version works fairly well, and the js version works for anyone who just wants a phone number or email address.
There has been a slight (and I mean slight) improvement in mobile-based traffic/enquiries, and as far as I can see no effect whatsoever on Google (or other search engines). I was/am more concerned about the possible negative effect of having some hidden elements in the mobile css version, but so far this hasn't had any apparent effect.
All the new css pages were spidered and indexed before Christmas, so I imagine any effects would have been noticeable by now.