In the company I used to work for we covered quite a range of development targets, from embedded micros up to very high level factory control systems, and I alw

In the company I used to work for we covered quite a range of development targets, from embedded micros up to very high level factory control systems, and I always found the most challenging stuff was "in the middle" - stuff at the systems level. At the bottom, it really felt like programming a machine, and I found it all good fun, much like solving a puzzle (with occasional obscure headaches, mostly compiler related). At the top everything is pretty abstract, and there's more freedom to do conceptually interesting things (for example we were doing quite a bit of adaptive control type stuff, which would have been a nightmare to write with lower-level languages). In the middle, however, it seemed to me to be largely just a complicated network of interacting conventions. Those systems are neither firmly grounded in "reality", because they are generally trying to abstract away those details, nor are they "theoretically pure", because they need to be efficient (though there is a lot of interesting stuff there). What that means is that you simply have to learn and understand all those human-defined conventions to know what you're doing, and that makes solving problems at that level more difficult, or perhaps rather it requires much more hard-won expertise (which I never got much of - I just bugged other people until they would help me out!). Obviously, my views are coloured by my personal experience, so make of them what you will.