It used up to 60% of the bandwith while I used either/both LimeWire and IE.
It does not 'use' bandwidth, it scans it. It works like a proxy, all traffic (http) passes through it to be scanned.
Mod: I would also like to know if the built-in processes of the On-Access Protection Control use their own executables
Yes. ashServ.exe is the Standard Shield; ashMaiSv.exe the Mail scanner; ashWebSv.exe the WebShield. Other providers uses ashServ.exe as well.
and what the different Avast! executables (like ashWebSv) actually does, as I can't seem to find information on this anywhere else. Would be nice to know if I want to do anything related to these exe. files (allow access/block/terminate etc.)
Do you mean into the firewall settings?
C:\Program Files\Alwil Software\Avast4\ashWebSv.exe (avast! Web Scanner)
C:\Program Files\Alwil Software\Avast4\ashMaiSv.exe (avast! e-Mail Scanner Service)
C:\Program Files\Alwil Software\Avast4\Setup\avast.setup (avast! Update executable). This is a temporary file that just appears when an update (check) is about to launch, and disappears again afterwards.
Don't need rights to connect:
C:\Program Files\Alwil Software\Avast4\aswUpdSv.exe (avast! Update Service)
C:\Program Files\Alwil Software\Avast4\ashServ.exe (avast! antivirus service). Although, ashServ.exe sends ping packets to find out if the Internet connection is alive. You can turn this off by checking the "My computer is permanently connected to the Internet" box in the avast Program Settings > Update (Connections) page.