If you have multiple cars and lots of maintenance - this is an absolutely GREAT kit to have. Sure, they arent as light as titanium, but they are strong, well made and the hex heads wont strip easily !
Great place to start swapping old (Tamiya) Phillips screws is on the chassis bottom (typically flathead, countersunk screws) as they get worn easily during contact with stones, road bumps etc. The hex screws wont lose their hex shape - and so can be used and reused easily. Just make sure you have a good set of hex drivers !