Actually, I have found double hand casting to be very "user friendly", if by that you mean relatively easy to acquire the skill. If you have a good basic understanding of single hand fly casting, you will be able to pick up double hand casting without much problems. The first few times that I was out with a spey rod, I was able to double spey or snap-t the head of my spey line...which is roughly 65'. It took me a LOT longer to be able to cast 65' with my single hander when I was first starting out a long time ago. Many people on the water can't even cast 65' effectively. So in my books, spey casting can be learned relatively easily if you already have good fly casting skills. Just don't expect to be shooting running line the first few times out.
There's several advantages to double handers. 1) You don't need a lot of room behind you for a back cast...so brushy riverbanks are no problem. I heard that using the newer RIO Skagit lines virtually doesn't need any room behind you for the D loop. 2) Your fly spends a lot more time on the water, and usually that means you stand a chance of hooking more fish. Spey casting is very efficient. Instead of flase casting and stripping your line, you do a simple modified roll cast and your fishing again. 3) The longer spey rods offer lots of line control and control while fighting big fish. You can do large mends more easily to control your presentation. 4) Casting a spey rod and fighting big fish with spey rods are a lot easier on the body than on a single hander. Your shoulders and arms will thank you for it. I refuse to play large springs and chrome chums on my single handers. I only fish for them exclusively on my spey rod. 5) It's just plain cool.

Of course, spey rods are not very effective in slack water where there is no current to drift your fly. You can cast and strip a spey rod setup, but their large size makes them feel unwieldy when used in this manner. But for fishing large salmon and steelhead on the flow...there's nothing else like it. I'm still relatively new to double hand casting myself...but I'm having a great time learning and catching fish with it.