I have a Seagate GoFlex drive. I am considering whether to get the USB 3 version or the Firewire one.
I thought the point of GoFlex drives was that you could buy different adapters - so you could start with Firewire and swap it for USB 3.0 later?
I know that a few companies have made usb 3.0 card for the MBP 17".
Are they good for working under both Mac OS and Bootcamp Windows 7?
That's something you should check with the vendor, but since these are almost certainly re-badged generic cards made for the PC market, they are highly likely to work under Bootcamp Windows. Since its an ExpressCard connection it ought to be fairly fast. I'd be more worried about the
restrictions on the OS X side - storage devices only, no bus-powered drives, no hubs...
(Also, you may also need something like Paragon NTFS for Mac and/or HFS for Windows if you want to use an external drive on both - otherwise the only format that both can read & write is FAT32 which is fine for USB sticks but not so good for a large hard drive).
If you have - or are considering - a MBP 17", bear in mind that all the current "coming soon" rumours seem to be about the MBP 15" - it might be a while longer before there's a desirable update for the 17". People buy the 17" for screen real estate and extra expandability (ExpressCard and an extra USB port) so a more "Air-like" version with fewer ports and a "retina" display (its half-way there already) doesn't really make sense. I wouldn't be surprised to see it either dropped or just given a minor speed bump to keep it going.
Seriously - I think your best bet is to get a drive which can do both FireWire and USB3, and use Firewire until the new Macs arrive, since the one thing that Apple would be
totally insane to do is produce a new MacBook Pro with neither of those (unless they also launch an affordable Thunderbolt dock). If you already have a GoFlex drive then you're halfway there anyway.