RFTools adds a tech version of dimension creation, which actually tells you when you've made a grammar error. But it doesn't just add dimension creation. It has customizable screens, interesting power generation mechanics, redstone logic, tech-based teleportation, and more. I'm sure @McJty can tell you more.Ehhhh, please respect the amount they've been integrated into quests and scripts. Also, Mystcraft > RFTools.
I'm not saying swap mystcraft with RFTools. I'm saying add it in as the tech alternative. Mystcraft is great for magic players, but the techies do better with RFTools. I mean having a totally teched up base but relying on portals and books for teleportation sort of ruins that. RFTools is great.