Andy_Panthro: Whats wrong with "proper" externals?
I've got a 250gb western digital, formatted NTFS so it's drag and drop (no software required, just works through windows explorer).
Works really well for me to backup my music, photos, savegames etc.
Transfer speed is significantly lower for externals (60 MB/s for USB 2.0 vs 300 MB/s for a SATA drive). Not much of an issue for just occasionally mirroring files, but can become a bit of a bother for common use. Personally I use an internal drive to store everything that isn't an installed program, then mirror that internal drive to an external drive every couple of months for backup purposes.
But back on topic, my plans for Dragon Age are to wait for the GOTY edition that will probably contain all the inevitable DLC. Although my plans may easily end up changing once it's released and I'm able to read what people have to say about it (of course changes in plans could go in either direction, from "buy it now" to "I'll pass").