I see this posting is pretty old but here's my experience, for what is worth.
I bought today a Toshiba Canvio 3.0 1Tb and I have both PC and Mac at home.
For 90 $ at Radio Shack I thought it is a good deal although it did not say on the box very much.
It was formatted NTFS and had some software on it as well as a manual.
I tried to mount it first on my Mac OS 10.7.4.
Without any drivers and with it's own cable it worked at first attempt.
I could copy some music to it and it just worked fine, I could play it.
Then I read the instructions and it says you must install the Tuxera NTFS driver supplied on Canvio to work read/write otherwise will be read-only.
Once I did that I attempted to copy and it shown some activity. Then I decided to reboot as indicated by Tuxera software and after that it only mounted in read-only mode. I tried to deactivate Tuxera, uninstall, reboot, reinstall, reinstall, reboot again, nothing helped. The Toshiba web site did not help at all.
Eventually I thought to try reformatting it and use it with HFS+. I copied all original content somewhere on my Mac for backup then started Disk Utility and opening the Canvio I noticed it offers a format option as Win NT NTFS Tuxera, which I thought to try and that worked indeed. Then I copied the original content back on the newly formatted partition. I can use it perfectly fine on my Windows 7 as well as Mac. It works pretty fast.