While I love my Bugaboo Cameleon, it is not great on the tube or for travelling. I have therefore looked at different light weight buggies.
The most popular ones seem to be the Quest and Techno XT by Maclaren and the Baby Jogger City Mini. The Maclaren Quest (http://uk.maclarenbaby.com/toddler-buggies/quest-sport) is light (5.5 kg) and comes in great colours (after all the buggy also has to look good!). However, it only has four recline positions, its wheels are not particularly sturdy and the seat has not much padding. A much sturdier and more comfortable buggy is the Maclaren Techno XT (http://uk.maclarenbaby.com/techno-xt). However, it again has only four recline positions and at 6.8 kg is not that light. The Baby Jogger City Mini (http://www.babyjogger.com/city_mini_lp.aspx) is a pretty cool looking buggy but with 7.6 kg is not that much lighter than the Bugaboo Cameleon (8.6 kg) so not such a great option for tube or travel.
I ultimately went for the UPPAbaby G-Luxe (http://www.uppababy.com/products/product.php?id=171) which is very similar to the Maclaren Quest, just slightly lighter (5.1 kg) and with better wheels and padding. Furthermore, it has an infinitely adjustable recline from upright to 120 degrees, an extended SPF 50 sun canopy and comes with a coffee cup holder! The only downside are the slightly boring colour options - black, red, yellow or blue. I took it for a spin today and was impressed! Going up and down the steps in the tube was no problem. I could easily lift it. And, most importantly, the Baby who was facing forward and therefore had a great view of the world around her loved it!