I have done a ton of research into this type of thing due to the fact I can't get normal Cable/DSL where I live. Tried satelite, different cell carriers etc..
Satelite blows! The lag time or "ping" time is excessive! With the 1.5mbs premium package I was only seeing download speeds of 500kbs max.
My advise, buy a Verizon Mifi or a Verizon 3G USB modem(no longer available direct from verizon - use ebay) and a Cradlepoint router. Similar download speeds but upload speeds are greatly increased (3x+) and the "ping" time is cut in 1/3rd.
The Verizon Mifi has a limited range of like 25ft (line of site) so it doesn't work well for a whole house network. but I suspect that it would be the ultimate for in car usage.
For my home use i am using a Verizon 760 USB modem and the cradlepoint MBR900.
Honestly if you go with a setup like that in your car you can alsouse it in your home if you cable/dsl goes down you can use the verizon as a backup.
No I can't stream youtube videos but i get done what I need to online.