Big thumbs up. My son is four and only just potty trained, and scared of public toilets. This potty has got us out of several sticky situations. The potty is definitely technically too small for him, and even my 2.5 year old looks a little bit large on it, but both of them manage to get their wees into it (4 year old crouches over it and has a good aim), although no poos done in it so far. I should say our other potty is a chair-potty so I'm used to looking at bigger-style potties - I'm always surprised at how small 'regular' potties are. I only knocked a star off for the size.
It's really easy to empty and clean/wipe down, and totally leakproof, and I love the eco-friendliness. We've had it for 4 months and it has been indispensible. It goes on all trips out. We even used it in a quiet aisle in B&Q.
Rough potty-bowl dimensions; Inner bowl (the 'hole'): 14cm diameter x 10cm deep. Outer bowl (the bit they sit on) 20cm diameter, with about 1cm more to the outer edge of the potty.