Hi,
I'm currently in search of the 'perfect' (they never are, of course) Single-Double buggy for my two DSs - 2.5yrs & 8mths. The elder is at nursery two days a week, so I'd really like something either convertable (double-single-double) or not too bulky as a double (DS1 is not that keen of a walker).
I currently have the BJCS and absolutely loved it - it was perfect in the city, on the tube, fit everywhere and was great to push... until we moved to a very hilly suburban area - I now find it very difficult (if not downright painful - had an operation recently on the wrist) to push it up and down steep hills.
So... I find myself researching buggies again, but with a different list of criteria. I don't really need it to fit through narrow tube lift doors, on escalators or buses. What I need is something that would not kill me pushing up and down steep hills, would do well with occasional off-road walks (nothing too harsh), and would have reversible seats. I'm not asking for too much, am I? :) 
I'd appreciate your suggestions and advice!