RE: Baja 5b SS
I was asking the exact same questions before I got my SS! I was most concerened about what would happen if it ran away, after somehow loosing signal and running into some kid and breaking his leg! So I bought a failsafe, not sure exactly what it does because It hasn't been used yet but you deffinatly need one, especially with a thousand dollars cruising around a field!
As far as speed goes it is basically as fast as my (newer model) 3.3 Revo. So If you have some buddies with nitro cars such as the revo jato or savage you will be keeping up with them. If not faster, (but maybe since it is so big it seams faster). I have to say they are no question of a doubt THE most fun rc to drive EVER.
Oh and im using a spektrum dx3 because it has very good range. Farther than I am willing to drive it to be honest!
Hope you end up getting one there the most fun ever!