Thanks Naz good answer
All I can say Dave is that mine have lasted me longer than the socks I made from cheep £10 mountain bike tyres but I am about 17 1/2 stone fully clothed so I tend to scrub more rubber off just like a heavy car goes through tyres quicker
I have never used my PJ's without socks of some form so I can only say that the grip is better than any tyre I have used and I had no grip problems in the tunnel to the toilets at speakers corner (I actually bounced a little there, ask Paul if you want a laugh I must have looked silly doubled up)
tundraH and Paul seem to have done more hours on them than I have (40 hrs Paul have you turned them round yet or are you still on side 1 ) and both seem happy with the grip level
The sock version gives 2 ends to use whereas the Hoofies only give one but look better
so the socks are better value but for some looks are more important
(I wear £3 tesco jeans to get me to pay £100 pounds for a pair of jeans I would need sedating and then I'd fight

) but some people do
I have now changed my socks to Hoofies (for testing )so I am restarting the wear cycle again but if there is enough interest in Hoofies I will bring a spare pair to the next London meet that I go to and people can try them out
I must say that you are either light on you feet or have found a very good type of tyre as all my tyre socks lasted about 10hrs before they went through but like I said I'm hard on anything even shoes don't last long