I have a KME system and like it for EDC knives. I'm a novice with stones as this point but learned a lot about sharpening in general with the KME. As a stones novice I also found it to be quite useful to fix amazingly bad bevels on some cheaper knives ... Chicago Cutlery steak knives to be specific. However, I think I could do that just as easily although not a precisely with stones now.
Re low degree edges - definitely a limitation but I've been able to go to about 11 degrees (just as a test) but I don't see myself ever needing or wanting to go below that anyway. I'm just a home kitchen guy who thinks 16 degrees is just fine for my personal use.
KME also is not great with longer blades - I personally wouldn't use it for anything over 6 inches. You can but that doesn't mean you should. This was actually a driving factor for me to get into sharpening freehand with stones along with just wanting to because I think it's a cool/fun thing to do!
Practice knives ... I've found some great (German/Chinese) junk at the flea market for $5 to $7 to practice on, wreck, and practice on some more. Also found some stuff in my MIL's drawer. Both provide great chances to do broken tip repair, chip repair, bevel setting, ... etc. When sharp, run it over a brick or sidewalk a few times and do it again