I have been a OSM contributor for just over a year and have created my fair share of new data. I started out using Potlatch2 on my slow Toshiba laptop and then migrated to JOSM after about 2 months. The migration to JOSM has been worthwhile and I can safely say that I am experienced in it if not yet a super advanced user. In JOSM I now use filters, most of the keyboard shortcuts and a few plugins to easy my life. I also really like the shortcut to give me full screen editing without the clutter.
I have since upgraded to a well specced Macbook on a fast internet connection with increased concurrent connection settings in JOSM for quicker download. I have bought a R.A.T. 7 mouse for general usage and have played around to program frequent keypresses used in JOSM into my mouse. I have considered getting a programmable keyboard and possible another screen or even a touch screen. The idea is to use a touch screen with fastdraw JOSM plugin to more quickly trace map data.
However I still feel that there is room for improvement. I am curious to learn about other people's efficiency optimizations and tools and shortcuts you find useful and would be grateful if you could share some tips with me.