I no longer use ST due to being in the terminal most of the time, but one thing I miss is how easy it was to write new packages with Python. Just enough of the API was documented and exposed to get what you needed done and usually resulted in a plugin with pretty good performance. It took very little time to write things I missed from emacs like "sort paragraphs", opening files by typing a path, an auto complete that uses a similar algorithm. Even a ctags module that I wound up prefering over emacs. I think ST's extensibility is easier than just about any other editor I've used (I do develop primarily in Python though)