I'm going to agree that it's the programmer in you - in my experience with being a MapTool contributor and user, one frequent request was "give us dice we can see" (in other words, give us a dialog, a window, or even "physical" dice we can throw across the screen). I am of the opinion that typing roll commands into chat is the harder (or more inconvenient) way to do things, but I also understand that not everyone shares the opinion.
With regard to macro autocomplete, I had no idea it did that. Most of my macros are similarly named, though, so I'd need to type them out almost all the way anyway (I have dozens to support the game I was running, even as simple as it is).
The bottom line, really, is that personally I don't want to have to type a roll command or macro - in fact, I don't want to type anything - more than once, if I can avoid it.
The screenshot below is from my setup for Barbarians of Lemuria for MapTool, and in that case, I wrote the macros (the buttons on the left; writing a macro in MapTool includes creating a button to run it) one time, and from that point on I need do nothing else but click the appropriate button to make the roll and output the result in chat. I very rarely have to use the chat window for anything but displaying rolls results or the occasional emote or in-character speech. The buttons are also just faster, as far as my experience goes.
I'd love to see that kind of thing in Roll20 (not the dockable windows and extensive scripting language cruft that MapTool has, just the "creating a macro creates a button" part), assuming it's compatible with your design goals.