I have had a i'coo platon duo which turns into a single pushchair for the past four years. They are absolutely wonderful. They are very easy to push, its like steering on air, they can even be steered one handed when two up unlike most other doubles. They are very robust and last a very long time. The seats come apart for washing and they always wash up well. They are on the heavy side although they now make ones that are light weight. The basket is extremely large on the pushchair I had and there are not many products on the market that can be used as both a single and double pushchair.
I'coo are extremely reliable pushchairs and I am now looking to purchase another as I have not found anything close to the quality and versatility of these pushchairs. There are so many combinations of products that you can add to the chassis that you really can devise the best combination for your lifestyle and needs. I wouldn't say that the larger puschairs would fit into very small cars but they do make smaller pushchairs as well, although the larger ones do come apart into two pieces which is the easiest way to collaspe the product that i had.
I would buy I'coo again and again.