Finally got round to upgrading my phone and pad to iOS 7, wow loads slicker, well done Apple. Only problem now is I need to update my iTunes now so I can use it but....MacBook software needs updating too!! Trip to the Apple store to buy Snow Leopard required!!
If you're upgrading from an older version than Snow Leopard (where Mavericks isn't free) then you can just buy Mavericks for £14, which is the same price as Snow Leopard anyway.
Not actually upgraded to Mavericks yet so I don't know but would imagine the newer the better. Only thing to maybe consider is if you have an older system is the performance might not be as good, a RAM upgrade should fix that though.