Earlier quoted context omitted.
Where does a web-dev turn to to get started in this as a hobby?
No matter what you do, you NEED tools. I cannot stress this enough. If you can spend $250-$500 on a nice desktop scope, awesome. If you only have $80, you can get a serviceable Hantek USB scope that will at least give you an idea of what you're doing. If you can only spare $20, you can at least get an el cheapo JYETech scope. In addition, you'll want to pick up a multimeter and probably a logic analyzer. Again, no ne…
I wouldn't say that. Yes the Arduino "libraries" abstract away a lot of the complexities and hinder true understanding. However for a beginner it is a perfect platform simply because of the huge community i.e. tutorials, code and projects. Once they gain confidence from using this, they can move on to "traditional embedded development" by learning to program the underlying AVR directly i.e. use the toolchains installed by the IDE, delete bootloader and upload your program using the ISP interface (see the book; "Make: AVR Programming"). This gives you the best of both worlds using the same development platform. Another advantage is that many other MCU families also provide a "Arduino-like" interface (eg. Energia for MSP430) and thus all the skills learnt on one can be transferred to another.