Anyone got one of these? Or anything similar even?
After a marathon session last weekend that left my hamstrings quivering the next day i think this might be a good idea.

Or this
Naturaly the yanks go for something just a tad bigger and brasher.
Now all this squating down to work on the bike is great exercise i'm sure and hey i'm a superhero so i'm fit enough to take it of course, ahem.
But what i wanna know is how good the wheels on these thigs are and are they really as good as i'm imagining or just get in the way and topple over at the most inconvenient moments??