Obviously the driver software
You can get gribs and emails through a program called Onsatmail, it's a free download. (Don't try to download it via the satphone though)
Then you need a program to view the gribs - Open CPN
Speed - the size of the file will depend on what you specify on your grib request, I'd generally get one file in about 1:30, but a fair bit of that time was just logging in. I'd usually get 2 files in under 2 minutes.