Are they reliable and are they worth the money? That's a subjective question but as I currently own 5 Hobies, each with the Mirage Drive you could say I believe they are indeed reliable and worth every penny.
If you're humping and bumping along shallow, rock and shoal filled rivers then I'd say get something else. But anywhere you have the depth to use them (consistently more than a couple feet) they're tough to beat.
If I could only own one boat, it would be a 13 foot Revolution. If I did need to use it on a shallow, rocky river, I'd pull the drive and set the rudder to kick up and go on about my business.