I believe I tried it, and felt slightly better performance, but still lower than that of fglrx by a good bit.
As for the NI parts in your laptop -- along with using DPM (which will alleviate core meltdowns and any clocking issues (if they were affected; they might or might not have been), the r600g sb shader optimization will greatly improve performance in a number of apps, bringing it close to (and in some instances, better than) that of catylst/fglrx's. As they say, mileage will vary, and, in particular, I have no idea how effective it will be with your situation (GW2 under Wine). The sb backend is enabled by default in Mesa 9.3 (i.e. current git). If you're using a 9.2 build of Mesa, while it would have been built with support for the sb, it would not be enabled by default, so you will have to enable it yourself via the ENV Var (R600_DEBUG=sb).