We bought one a year ago (used to be called the maxi taxi). I wanted a lightweight 3 wheeler which took a buggy board and was easy to maneovre. The quinny easily does this and is really a dream to push. it has an extending handle which is great for DH as he has a much bigger stride than me and doesn't hit his feet on it when pushing (unlike our previous M&P pushchair). Because the wheels pop off I can easily fit the Quinny in my Yaris - another important criteria for us.
We had our DD2 in it from newborn and she was very cosy. The only slight drawback now is that the most upright position isn't that upright (not compared to some strollers) and DD2 constantly tries to sit further forward without resting her back on the pushchair which does frustrate her a bit, so sometimes I put a jumper behind her to help sit her more upright.
A good plus point is that the pushchair seat is quite wide so as DD2 grows she won't be so squashed in as some pushchairs are really quite narrow. however - because it is wide it can be a pain in busy shops.
The Maxi Taxi is now being sold more cheaply (we paid £200) as it's been superceded by the Quinny (which on a quick inspection doesn't look any different) and I recently saw the MT advertised at the Glasgow Pram Centre for only £139 inc free delivery.
Nearly forgot to add, that we also used it with the car seat attached which I loved. It took some of the faff out of a trip to the shops.
Anyway, hope this helps you with your decision making.
Jenny