I agree, Karin -- I like having my horses right where I can keep a close eye on them, and in the van they get a smoother ride and air conditioning (not to mention their own stereo controls, LOL). We do plan to eventually buy a big van with a permanent safety barrier and dividers, but for now our Ford Windstar works very well.
I do agree with Lisa of Ruff n Tuff that those transporting in passenger vans need to consider safety with a good safety barrier behind the passenger area and sturdy wire mesh/hardware fabric over the windows...also remember that the idiot drivers out there don't know that you have precious cargo on board.