chainless bikes - If damage to cloths is your #1 concern go chainless. Chainless also improves reliability and reduces maintenance for those allergic to chain lube. Shaft bikes have automobile style lubrication ports that work with a grease gun, do it right and you won't even see the grease. A bike with a chain case would work as well though. All chains will require replacement after a while, I suspect that shafts will work for at least one human lifetime. The belt on the Strida is a definately working on that bike.
elliptical chainrings - I have one on my fixed gear, I have nothing negative to say about it. The free market has spoken and nobody from consumers to professional riders endorse it. Perhaps with an aging population they might find a market. I think on single speeds they make more sense.
Pretty much there isn't anything better - I suspect hydraulic, and maybe even compressed air, drives might change things. Hydraulic is already successful with brakes. The Nuvinci hub uses 'traction fluid' and is successful, so I think you will see various hydraulic designs. Electric and other boosters might also change things. Automatic transmissions are showing up too.
airfree tires - For short distance commuters who cannot tolerate a flat, otherwise they are inferior.
2000 Montague CX, I do not recommend it, but still ride it.
Strida 3, I recommend it for rides < 10mi wo steep hills.
2006 Rowbike 720 Sport, I recommend it as an exercise bike.
1996 Birdy, Recommend.
Wieleder CARiBIKE (folding), decent frame.