Yeah, the 32-bit binary is i686 actually, but same difference. The binary is designed for compatibility and ease of use rather than speed, although the 64-bit client is compiled for speed too by default. Compiling yourself will get you a faster client, the ebuild will probably have the same effect. In future we'll probably spend some time making everything more 'standard' in the sense that our config files are put in the right place and such (so we can have per user settings for example). Then it'll be easy to get an official ebuild put in portage.