How does one know if upgrading OS will slow down their relatively older machine?
For example I bought a MacBook Air a couple of years ago. It came with Leopard and I've already upgraded to Snow Leopard, but now want to download Lion. I'm concerned though that it may slow down my machine.
I've heard of this before where upgrading OS slows down performance on older hardware.
How can one know if they risk a slower performing machine if they update OS?