I've got one of the faux leather wallet cases that opens sideways. Pretty decent I think, as it covers the back, sides and the front so can be carried in pocket with keys and not worry about scratches.
Pros
Good protection
Looks smart
Can carry a few cards and notes in there, although it makes the wallet thicker and the magnetic strip that keeps it locked is not as good, so 1 card is the maximum unless you don't mind it not locking as well
Cons
As above with the number of cards you can carry
When the case is open it can make it awkward to carry unless you fold it under, in which case it makes the phone bulky
Tricky to pull phone out of pocket with one hand and open the case and fold it under
But for £4 from ebay I'm not complaining, I like it!