After 2 happy years with the Rimowa Salsa, which has been almost unchallenged in its role as the perfect carry-on (My wife bought a Salsa Deluxe which has the small benefit of a strap for carrying extra items piggy-back – probably what I would go for if buying now).
I have now seen the Salsa Air – http://www.rimowa.de/main#product/822.52 – which is 1kg lighter – down to 2.4kg. It has the same overall dimensions – fittingthe smallest carry-on checkpoints. It also has a single strut pulling along handle – releasing a bit of extra space inside the case.
There is a great article here: http://www.philstar.com/Article.aspx?articleId=557631&publicationSubCategoryId=86
It has the 4 little castoring wheels instead of the 2 “skateboard” type integral wheels. The question is – is it strong enough to sit on. I will have a look in the next few weeks.
The other quirk is that it has two “zippable screens” across the two halves – making it harder to get items in or out – unless the zips are left open, but they also leave behind 4-5cm of “material” as a rim round the edge – which may have to be cut away.
The only other current contenders are the Zero Haliburton 21″ Carbon Fibre Carry-on($2,750) – which is too big to meet IATA carry-on regulations (at 33 x 53.3 x 22.9 cm) and the Tumi Vapor (similar price to Rimowa at around $500) which again is too big at 51 cm x 35 cm x 23 cm and actually has a full litre (thats two small bottles of water) less interior space than the Rimowa (which is 35l).