With the luggage fees imposed by Air Asia, I'd rather save the money towards actual travelling expenses. The advantages of light travelling outweigh the cons, and I like the fact that it 'forces' me to plan and think of what to pack. Instead of just chucking things into the bag like I used to. Bleh, I was so ignorant and blur = lazy.
What I like most about travelling with just one backpack is that it is easier for you to move around, your hands are free and the weight is spread comfortably on your shoulders. And another big plus is that you need not wait for your luggage at the carousel in the airport, you just whizz by after the Immigration :). Especially after a long flight or a delay.
I always bring another small slingbag for the purse, phone, camera, tickets etc. This helps a lot as I don't have to take off my backpack to fumble through the pockets for all these little things.
Until recently I used to death a brandless backpack I bought from Parkson in 2002 or 2003. The zipper gave way, the rest of it still in good condition. For the price I paid, 5 years is a good lifespan.
My current backpack is a simple High Sierra design, expandable by about 30% so that helps with extra stuff and purchases. Good for a 3-max 4 day trip, it probably fits about 25 litres or so full size, I think. In future I think I might get one that's slightly bigger, if I see one that I really like at a pretty price. Those high-end ones are really nice. With very pretty price tags too.
I have been discovering best ways to travel light through trial and error.
And I'd like to think that I have almost perfected the art of travelling light; in truth I have not mastered it yet actually. Some days I find that I end up with things I don't really use and I bring them just because. And some days I forget things, like sunblock (I have 3 bottles now, duh)
Am currently doing some homework to prepare My Ultimate Packing Checklist. Will post when it's ready :)