I wanted the 650 but only if i could get it for around £30, got tired of looking for an offer so went for the cheap 300 version for £17, sure it doesn't have the screen or more than one basic macro but to be honest i doubt i would really use those and it sounds like they could fail to work properly, should have better battery life as well.
As far as I know the 300 is a different class of remote, it doesn't do anything the other harmony remotes can, it's just a basic all in one remote (although if thats all you want then i guess its great for your needs)