Yes, it is USB based. Now the DIR-655's USB port can work as Network USB and 3G USB Adapter, as well as the WCN function.
This firmware is working great as of now. I noticed a stronger wireless signal with my MacBook, although when I was testing it with VoIP, it sometimes dropped the connection for a second or two.
I would like to try the NAS function, but I can't find the necessary software for accessing the network devices. It seems to be included in the DIR-825's software CD only, as I couldn't find it anywhere else. Looking at Lycan's reply as I was writing this post, I guess we will have to wait a few days for the software to be released. Anyway, thank you for your support Lycan.