No better time than the present! The ER-301 firmware is not like upgrading a cell phone OS where you can never go back. You can go back to 0.5 in about 30 seconds. It’s designed that way. Switch back and forth as often as you want.
So load the current 0.6 version. Load up all your stuff and see if it works. Report any bugs that you find so that they can get fixed. Ask questions if in doubt.
Just to be safe, don’t save any changes to your stuff over top of the old version. Save a new copy in the v0.6 folder that gets created. That way you can make sure the old one stays compatible with v0.5 for now.
There is a new way to install packages, the Package Manager, which you’d use for packaged mods (currently Accents and lojik). Previous custom units and chains install the same way as they did before, though they will hopefully also get re-packaged as “packaged presets” by their authors for 0.6 at some point.
EDIT: 0.6 is pretty solid btw. I can’t promise you won’t find a bug somewhere but if you do and report it, it will probably get fixed pretty quickly.