Yes, I use a 85W charger with my MacBook Air everyday (I have several 85W adapters). In fact the adapter runs cooler as a result.
When buying a replacement or additional power adapters, always pick the 85W because the 85W can power all the MacBook Pro and Air portables, whereas the 60W can only power the 13" MacBook Pro and Air, and the 45W can only power the MacBook Air.
The only advantage I see with the 45W unit is that it's a tad smaller.