Billysugger:
whether to invest my time in a tool.If the sketch system and the Arduino IDE are prerequisites for using the Arduino architecture, then can anyone make the case for it for advanced users?
I suggest that it is well worth investing 2 or 3 hours just to experience the system. I wouldn't dream of recommending the IDE for editing code, but it is an option in the preferences to use an external editor. If you select that option the IDE just loads the latest version of the file before it compiles and loads it.
What attracts me to the IDE is that "it just works". Plug in an Arduino, upload the program (sketch in Arduino speak) and open the serial monitor if you want to see output in a simple format.
Another important factor is that using the IDE will make it easier to take advantage of all the advice on this Forum as most people here also use it. You will be able to post sketches that others can compile, and vice versa.
I have no idea what an "advanced user" is. I am advanced in age, but not in mindset (I hope). My sense of "advanced user" is one who gets results with the minimum of effort. (Another interpretation might be a person who doesn't use C if s/he can avoid it)
What do you think you might like to do with an Arduino that could not be done using the Arduino IDE?
You may have the impression that the Arduino is a toy system because most Arduino sketches are contained in a single .ino file. However the IDE can easily work with multiple files for more complex projects. The extra files can be .ino files or regular .h and .cpp files. And the size of projects also reflects the very limited resources available in a micrprocessor compared with a PC.
Bottom line ... take some time to "suck it and see"
...R