I personally haven't seen the Air movie, myself, so I wouldn't know how good it is. I heard it's better than the Clannad movie (hard to be just as bad or worse than the Clannad movie, though), so I might watch it later.
IMO, Air is similar to sola, but slightly inferior (but it's still good).
Similarities include, but are not limited to...
Both are 13 episodes long with 2 OVAs.
Both have to deal with the characters' past selves from centuries back, and details are revealed little by little.
Both have, IMO, a very similar feeling to it (like they give a similar aura, if that makes any sense).
There's other stuff, but I'll spoil if I say them...