I use the one which comes with Kudesnik's Vista Icon Pack v3. It also comes with the icons for Floppy and CD\DVD drives so I think it's kinda better. Apart from the fact that it's not sleapstreamable and is built-in into the whole pack of course.
I personally use original awxTools installer with /VERYSILENT /SUPPRESSMSGBOXES /NORESTART options and a custom reg file to add more supported formats. What have you added in your installer to make it less "limited" (can't possibly think of anything else it should do :\) ?
Yeah, repacking lots of stuff could be a problem. Especially when you have locked archives... Anyway /s is like the only switch out there for SFX archives. Sorry
You need an install script for that (it's written in Comments field of SFX package). Use WinRAR help or search the forums for the thread explaining the command. In short if you want it to install to %ProgramFiles%\MyCoolApp you need something like: Path=MyCoolApp Silent=1 Overwrite