I tried crashplan on my macbook air. The big thing I'm noticing right now is it takes freaking forever to do the initial backup. I'm really hoping that subsequent backups don't take nearly as long.
The initial backup can be long yes... I usually leave my Mac always ON for a couple days when that initial backup is happening.
After that first backup is done all the others are incremental and usually fast... Unless of course you just created a multi gigabytes movies that need backup.