I have been riding a Brompton P6R for a little over a year now, and am very happy with it. I purchased it because a number of people and reviews told me that it was sturdy and well made. This, I have found to be true. I was concerned that the smaller wheels would make for a unstable and touchy ride, but this has not been the case. The bike has a very stable feel to it in all situations that I have ridden. It does not ride anything like a full size bike, but it took very little time to get used to the way it does ride. The other thing that I really like about this bike is that it folds into a very small package, which makes it easy to deal with on trains or in busy train stations.
You will notice from the pics that I keep a fairly large seat bag on the bike. NJ roads are not very clean, and flat tires are a reality of commuting by bike. I keep a spare tube, pump, 15 mm wrench, multitool, and patch kit in the bag. I have been able to change a flat in about 5 minutes, though this does bring my biggest complaint about the design of the Brompton - no quick release wheels.
Since May of 2010, I have put about 3500 miles on my Brompton. I commuted on it every day during the fall semester, and every day since mid February of this year when the roads were clear of black ice. It has also done a number of recreational trips to New York City, and most recently to the Niagara Falls area.
There are two other drawbacks to the Brompton that I can see. It is quite pricey for one. You can expect to pay somewhere around $1300 for a good one. This seems prohibitive, but you are paying for a design that is well thought out and executed. The other issue is finding parts. Since I live between New York City and Philadelphia, both of which have Brompton dealers, getting parts has not been a problem. I had a long conversation with someone from Hawaii, who refused to buy one because he had no easy source of parts. Since many of the parts are very specific to Brompton bikes, it's hard to argue his point. I have been able to use other brands for chain and bottom bracket, but wheels and cogs are very specific to the Brompton.
