I learned on white arkansas stones 40 years ago, then bought waterstones when they first came out in the early 80's, and actually wore one out (mostly used it for woodworking chisels and plane irons), and am on my third (2nd one froze in the water, and cracked) now. All hand, so I agree with all that one needs to learn by hand first - not hard at all. What's most important is having good eyesight to see the actual edge in direct light, so you can see that little white line of unsharpened edge. Once you can't see it, and it shaves, you nailed it. Angle is muscle memory / visual check.
Now I keep an Ultrasharp diamond hone in my pocket at all times - more EDC than my knives. Handsharpening skillset allows one to sharpen anything, anywhere, because you can always find a brick, a riverstone (Great mention by Antdog), or a slab of concrete. You can even flatten a riverstone on another larger stone first, if you really wanted to, then with the right skills (and right rock), you can shave with the results.
Guided systems are awesome though. I have friends that get into the zen of sharpening, take forever to sharpen an edge, then I take them to my shop and in less than one minute I manually hollow grind one of my chisels, hit it on my waterstone, then mirror the edge with white rouge, and shave with it. Last time I did it under 30 seconds. Freaked him out.