I've used gore systems on several bikes that have seen a lot of racing and I highly recommend them. You've got to follow the instructions and make sure you order the right set for your bike. Make sure you have bomber cable cutters - i like the ones from park tool. The most important aspect of the system is the ability to seal the cable system. This has allowed me to dial in four bikes at the beginning of the cross season and only do minimal maintenance throughout a season of weekly mud slinging.
Read jontu's review below - and note my reply.
You need good cutters, read the instructions (I'm sure jontu did) and I'd say that a dedicated road bike doesn't need them, and an internally routed cable system also doesn't need them.