We've covered this elsewhere, but the fact that the latest Mac version is now free for all OS X Mavericks users - even if you do have to pay £2.99/$4.99 to get all the content - is great news.
As for the iOS version, first impressions are that, beyond adding more tracks and Inter App Audio support, not a great deal has changed beyond the interface. Again, there's an in-app purchase if you want all the goods, but it seems that, if you've already paid your £2.99/$4.99 for the app, you don't have to pay it again.
Should I download it?
Mavericks-running Mac owners should definitely take it for a spin - it's worth having a play with for Drummer alone. iOS 7 is a requirement for the latest version on mobile devices, so you need to decide if you're ready to make the jump to that before you dive in.