And professionaly speaking...editing files (audio, video) usually happens on an external drive, the bottleneck then is the connection with that external drive. Unless of course you use a desktop (an optibay perhaps is another option, but this is the MBA forum).
Use-case scenarios vary. I use the MB Air as my main and only computerthe first computer I had that is both fast enough and really portable. Editing files in my case happens on my main drive whenever it's possible and if upgrading the SSD will get Lightroom thumbnail grid or previews to display noticeably faster, I guess it is worth it.
I wonder what the hit on battery life is in reality though.