compatibility usd external harddisk

[bas <bvpoppel casema nl>]

I conisder buying an external usb harddisk. I searched for several hours 
the internet, websites of western and seagate, and vendors. No one seems 
to give a clear statement on what model/brand works on linux. So, either 
there are no compatibility problems or there are so many problems that 
no one knows.

My (simple) question: can you buy without risk an extrnal usb harddrive 
from e.g. Seagate or Western ? Are there specific details to watch for ?