I put Limo in the rear windows and 35% in the front 4. Looks great from the outside but, the limo tint takes a bit of getting used to for night driving.
In Ontario, I have the lowest legal tint allowed: 5% in rear (rear windshield and 4 windows in back doors), and 35% front (4 front door windows). The difference in tint is noticeable at certain angles but, all-in-all, it still looks great!
I would still recommend going with the same tint in each window. This keeps the tint looking uniform. Check with local laws and use the lowest tint allowed for the front, as the all-around tint.
I would also recommend getting a sunstrip accross the top of the windshield.