drrobwave has had success converting his 7-sp 105 freehub to 8/9/10 and going STI. The bike is still full 105 and runs great.

I've simply swapped wheels to convert 2x6 105 to 2x9 105, changed the crankset to 9-sp 105 and added Tiagra STI's.

I'd love to have those older polished 105 hubs on a modern 8/9/10 ride, but I've not tried that yet.