G Data Internet Security 2011 unique feature is its DoubleScan technology. This uses two independent detection engines to scan suspect files. Engine A (Bitdefender) offers very good detection and very good perfomance while Engine B (Avast) offers good detection and optimum performance.
You can do a custom install to disable firewall if you've your own third party firewall. A bootCD can even be created to remove malware when your PC is not bootable.