1. Experimental aircraft can take passengers. After they are built they require a proving period where the builder flies it to prove it's safe. The airplane gets a certificate of airworthiness and is legal to carry passengers after the inspector looks over the plane and the pilot meets the minimum solo hours proving it's safe to carry passengers. Have you ever actually looked at any kit planes? Do you see any with more than one seat? I certainly do, including some of the most popular kit planes in the world, Van's Aircraft
http://www.vansaircraft.com/ . A kit plane does NOT have to be a certified airplane to be able to take passengers. They operate under the Experimental Aircraft category in the US.
2. IFR has NOTHING to do with built up and urban areas. This may surprise you but the big jets you see landing at a major international airport are often operating in VFR. VFR is visual flight rules, it means the pilot is responsible for see and avoid, as well as being required to be able to see at least x miles, which is different between countries and jurisdictions. VFR pilots can operate in controlled airspace, except class A which is 18,000 and above.
3. Ultralights are not limited to under 100 feet. Do you realize how low that really is? Yes you can not usually fly them over congested areas, but congested does not mean IFR. Ultralights may fly in controlled airspace, both class B and C, with prior permission. Ultralights typically fly out of a farm field or grass strip and generally those are in uncontrolled airspace, class G. For the type of flying one usually does with an ultralight, this is generally fine since they go slow and have a small payload. They are really for recreation anyways. I don't know why you would think anyone would WANT to fly an ultralight in IFR conditions. First of all you need expensive instruments which won't likely even fit on the instrument panel in an ultralight. Second, IFR conditions are usually cloud, rain, snow, ice, etc. and ultralights are extremely light weight(duh) and a lot are open cockpit. So what's the issue here? Ultralights fit many people's needs for recreational flying and are quite cheap to build and operate.
4. Experimental aircraft are making great strides forward compared to the FAA certified aircraft such as Cessna, etc. The engines are using half the fuel(such as the Rotax) compared to the certified aircraft engines(Lycoming, Continental). The reliability is also on par with certified aircraft engines. The same thing is happening with avionics. Kit planes are often built with full glass panel cockpits and much cheaper cost than doing it with certified avionics. They are just as reliable as the certified avionics. Having everything require certification makes the price 2-4 times as much and slows down the progress. For commercial operations, I can see the need for certification, and the piece of mind it gives people. But the EAA has shown for non commercial and personal flight, the certification does not give you much if any benefit.
