What were you planning to use your Air for?
Browsing, youtube, iWork, iLife (mostly iTunes and iPhoto, some iMovie), Textwrangler, some gaming (most demanding games would be World of Warcraft and X-Com). No heavy photo and/or video editing, no creative suite level stuff. Also some website management via CMS or lightweight desktop editors (something like Rapidweaver).
Nothing too taxing, really.
I know an i5 just has to be able to handle stuff like this with ease, but I sometimes tend to listen too much to negative feedback. I guess I should stop reading this thread