Although it is personal preference, I believe you should increase your shutter speed a bit next time. Yes it's nice having the wheels blurred and a sense of speed but having too much (IMO) makes it difficult to tell what is actually going on. I believe there is a fine line between showing the racer's speed and showing the skills they have to use to achieve that - does that make sense?
Here's an example using one of my own shots (forgive the small size!):
So I believe I have mixed the sense of speed (notice the tires are blurred) with the skill involved (the turn coming up, the driver's focus) to obtain the speed.
It's by no means perfect - if I could go back and do it over I would try to get an even larger sense of speed with a little more panning but I think it gets my point across.
With that being said, it's nice to get some crisp panning shots. In which case (not to be rude or mean or anything) I would have tossed #2 and 5 and considered #3 and 4 as very iffy.
This is my impression of what I would want my pan to be:
It's crisp, things are blurred but again, it's not perfect and I could/should have gone even slower but I was being conservative that day.
Your #1 is nuts. It's hard to tell if I like it or not but it certainly is impressive how clear the fellow's face is.
