Please forgive me for lacking expertise in forums, typing, etc. and for not yet finding the best way to post Youtube videos.
That said, here is one of the best developments in mutirotors IMNSHO:
Tilt Rotors !
I like these because they are not TOO difficult, and have been implemented with much success by a few people. I think these should become all but a standard in multirotor craft. Here are examples:
Youtube: iQuad tilt rotor test / close-up example:
Another iQuad tilt rotor, this one has a very nice frame, (and I am partial to using aluminum)
Another 'Angle Quad', this one uses carbon fiber tubing:
Here is an 'Angle Quad' / Tilt-Rotor in a good demo flight:
This is a 'T-tilt' Tricopter:
This is a cross breed between an RC plane and a multirotor as a VTOL:
(If this is the guy I think it is, he actually switches his remote from multirotor to plane configuration in-flight, which he says only tales about a second.)
There are varying degrees of success with tilt-rotors, but mostly success. One distinct advantage is that a multirotor normally has to pitch to about 45 degrees for a balance between forward speed, and giving the craft enough lift. With Tilt Rotors, the motors can do a lot of the pitch, giving the craft more potential dedication to forward speed.
Tilt Rotors have also been used for more specialized uses, such as one guy wanted to have video where the craft can 'Pan' directly sideways without tilting (yaw?) and keeping a more lateral and flat flight path as he goes to one side.
Another facet to this is that he had to invent/improvise a third joystick to operate it, which may seem to add more work and difficulty to it, but also shows more of the guy's innovation and genius:
This is a prime example of what I mean when I write about "advanced design and concepts", and taking things to the next level.