External portable usb drives - warranties and customer service - best & worst?

Hi,

I'd like a large capacity (anything larger than 320gb) USB portable drive I can use between machines. I don't intend on carrying it about too much, but I assume drives with rubber cases do serve a purpose, and shockproof is similarly not just a marketing hook?

Before I start I want to say I've read the threads mentioning WD drives, plastic enclosures, and mounting drive in enclosure yourself (never done that - but I'll look into it). No, as reading on line reviews can be confusing, I've decided to come at the question a little differently - i.e best warranties, and when things do go wrong, who's the most helpful & the worst.....?