The 11" MBA is an awesome machine - I bought one late last year, although it was the maxed out i7 8GB 512GB model, which is pretty pricey. My other most used machine is a 15" MBP from 2009, and I really don't notice the difference, as you focus on what screen is there. It's not like your attention is set at a certain area.
As for power, I haven't tried gaming, but everything else is fine. I've edited 1080 HD video and there is no problem with doing that. Sure, an iMac or rMBP would be faster doing the rendering, but it is plenty fast for all the real time stuff. It even keeps up when plugged into a 27" Apple display - it's possibly the only 'netbook' that lives up to the potential of the original concept.
The only things I would like from the 13" are the SD card reader (solved by just carrying around the USB cable from your camera/camcorder), and the battery life, which is only a problem if you are hammering the processor (solved by carrying the power supply, which you should anyhow).
The real benefit though is the size - It's like carrying around an iPad and then realising that you had pretty much all the functionality of an iMac all along. What really surprised me is that I bought it as a second machine, but it could be a main computer for many with zero compromises.
David