We don't own one yet, but I have read good things about the EZ Cruiser Lite and the Airhawk. I will be following this thread to see other comments.
We went with the EZ Lite Cruiser for our 8 year old. We had to modify it because he is a little small for it but would be perfect for a 12 year old. It's about 60 pounds and can be folded up and put in trunk.
We've heard the same about the EZ Lite being good for some applications, primarily light use and travel. There's no suspension, so per conversations with an EZ Lite representative and our physical therapy team, it's not suitable for use on a daily basis/as a primary electric wheelchair.
On another note, we're on the wait list for a 'used' one - sometimes people purchase one, but it doesn't fit their needs (eg an elderly person). So the product is returned. Buying 'used' is just like buying new - exact same warranty, the product is thoroughly inspected/gone over before sending out to it's new owner - but the buyer saves a couple hundred dollars.