Well its just a myth, dont worry, all 1TB HDDs work gr8, I Myself hv a 1TB (eSATA+USB 2.0) ----> Seagate BlackArmor WS 110 HDD and it works gr8 Dude..
Well afaik, Seagate FreeAgent GoFlex HDD (1TB and Above) come with a USB 2.0 but also hv an option of a Docking Stand for a USB 3.0 connectivity option (TO be purchased separately wich costs hmm.. i guess 3-4K) NOT worth buying it jus for that Docking Station (Stand)....
So, if DONT mind the USB2.0 connectivity and want a really light and Portable option than opt for a WD MyBookEssential HDD or a Seagate F.A GoFlex 3.5" HDD
(if u are concerned abt the life and working) Then buy the one wich provied better and longer warranty support
the Mybook Essential does need an external power adapter.
Moreover it uses a bridge chip which does on-the-fly encryption in hardware.What it means is that if your mybook goes kaput someday,you will not be able to pull out the hdd from the casing and hook it to your pc and copy your data.The hdd will work only inside the casing(unless you are ready to wipe out all your data).
Better avoid any external drive which does hardware encryption without giving you an option.