IMHO: They are absolutely NOT worth it.
First, the 33mm tower can only work with the rear folding sights. Together from HKParts, that will run you somewhere in the neighborhood of $475-500 shipped if you get the German rear. That makes KAC irons look cheap. And you can't mix and match with any other sight options and you will have trouble finding cowitness mounts if you ever want to run a red dot sight. The front sight is really thin, and with the post and protective sides, it looks like a tiny pitchfork and offers a rather poor sight picture. If you ever run a magnified optic, you have several hundred dollars sitting there doing nothing (the front sight if folded is taking a bunch of heat and carbon off that gas block bleed off valve port. You are also stuck using the short factory handguard otherwise the front sight is stuck under the rail and isn't usable.
Regarding robustness...I've had these sights before, but not long enough to put them through hard use. However, I saw areas on both the front and rear where I questioned their robustness.
But hey...It's your money