The maxi's are brilliant - we've found them to be much more stable than normal 2 wheelers.
The prices they go for on eBay are ridiculous - second hand they are going for more than £85 when you can buy them new for about £90!
We recently bought them for our 3YO triplets as the Maxi on its lowest setting is the same height as the Mini! It makes sense, money wise, to miss out the 'mini' stage and go straight to the Maxi :)