I've been using a 2.13 ghz Air with SSD for the past 1 year, and just bought a 17 inch i7 2.66ghz anti glare two days ago
The weight difference is huge, but so is the performance.. You'll need to decide yourself on what you intend to use it for.
The Air would be great for light tasks like email,surfing the net, minor photoshop. Even watching HD video on it would tax it already. Once the fans start kicking in, everything will start to lag. Even watching Youtube HD for more than a few minutes will kick the fans in and turn it hot.
The Pro just handles everything like a champ. I use just the intel graphics all the time and even 720p MKV files hardly make the CPU usage go up by much. 720p mkvs are unwatchable on the Air even with PLEX. They are smooth for the first 10-15 minutes, but once the processor heats up and kicks the fans in, the lag starts coming in.
And it's screen is vastly inferior to that of the LED screen of the pro.
Put side by side, the Pro's LED screen makes the Air's screen look really yellowish. I was shocked when I put them side by side to compare.
The Air's great because of it's weight. It's mega light and you can just carry it by pinching it with two fingers.
So decide what you intend to use your next computer for before jumping in