Depends on what you're doing.
Like I said, it depends on what you mean by "fast" (or "slow"). The benefits you mentioned are due to the SSD, which allows the UI to react well to opening apps and such, where harddisk speed is a limiting factor.
I'm not saying that the 11" MBA isn't a good computer, but if we're just arguing about the speed of the computer, then the MBA isn't fast, and it's due to the technology used. There's no way to get around the fact that it uses a slower processor, and as a result, will process data slower. It has an SSD, which makes the MBA usable (otherwise, it wouldn't be usable), but if you want a fast primary laptop, you should get a MBP with an SSD.
Even the old 13" MBA had an SSD and showed the same speed advantages you mentioned. Also, many people get an SSD to replace their MBP's harddisk, and notice the same improvements.
Personally, I want an 11.6" MBA (just like the OP), but only because I have an 15" MBP with an i5 processor that handles things like Handbrake really well. If I didn't have the MBP, and I wanted to get a primary computer, then I'd get the 13" MBA or a 15" MBP. There's no way the 11.6" MBA would be my primary computer, even if I had an external LCD.
Part of the beauty of having a laptop is the ability to use it anywhere, and that includes doing work. While some people can decide exactly where they will do work, many people can't decide that if they need to sit down and do work for long hours, it must be done only at their desk because their screen is too small to be comfortable. I do work at home, and at work (surprise!). When I was a student, I did work at the university library, in my office (I was a PhD student...), at one of the university's cafés, etc.