I love the flat pram, the pushchair part is brilliant (although DD is still a bit too little for it so we've only used it once). You can get attachment prong things so you can use it with a maxicosi car seat (if it's a maxicosi on an isofix base you don't even need to remove the prongs when you put the seat in the car! If you need to take off the wheels, that's so simple too.
I would only say have a think about whether you will be using it "off road" and if not, then go for the 4 wheel rather than the 3 wheel, because the 3 wheeler is a bit heavy on smooth surfaces like shopping centres.
I got mine on ebay a couple of years ago. Not sure I'd buy it again. The wheels have stained the vinyl on my kitchen floor (it was new ), it's heavy, takes up the entire boot of our small car, and the steering isn't always what it could be. Not that I'm going to the effort of getting another one for DC2! I contacted the manufacturer about the marks on the floor and was less than impressed by the response I got. Hopefully there have been some improvements.
However, it is one of the few which geniunely has adjustable handle height (great for tall Dads with dodgy backs), you can face baby backwards or forwards depending on mood, and has good carrying capacity underneath (which is what put me off Quinny).