Looks like a lot of us come to the same conclusions...
We are another Quinny Buzz 3 travel system user, with a Maxicosi Cabriofix car seat - you ened a base to make it ISOFIX.
As others have said, accept that the 1st year car seat is a 1 year item, and will be replaced.
Having one that fits the pram chassis (as ours does) is very handy for popping out quickly, think about new mummy on 9-12 months maternity desperately needing *insert baby item here* and you being back at work.
Much easier for her to chuck the baby in the car seat, run to the supermarket, on the chassis, round the shop and home rather than stuffing around with carry cots etc..
The Quinny collapsible carry cot is very good too, I can fit the chassis and collapsible carry cot in the boot of my Panda!
Erica has a Kari Me sling. She says it's great for getting stuff done around the house, but as others have said, 2 hours max as they get tiring and also pretty hot.
Nappy wise, if you're thinking about washable / reusable ones, look at Little Bloom / Yellow Bloom on eBay. A LOT cheaper than the brands, and of the 6 or 7 brands we have different versions of, including Tots Bots, they are best:
http://www.ebay.co.uk/itm/Baby-Washable ... 4ab243da72
Also, don't think these things need pins and boiling, we're talking about 40 wash in the machine, occassional hotter wash if they look bad, then pop them in the tumble.
Fitment wise, we're talking velcro and/or poppers, no harder than a disposable..