I've tweaked and added quite a few things to my MiniST2, some trivial, some major. I'd say the biggest and best would be the 35A controller upgrade from Area13, closely followed by a Redshift seat-suspension post and the Area13 hybrid mechanical-hydraulic brake calipers. But even the $13 much-louder mechanical bell to supplement the feeble factory dinger is very worthwhile, as are the mirrors etc.
I sort of went nuts over the last couple years accessorizing, but each had a reason to buy and a purpose to exist on the bike.
And howdy to the newbie from a fellow nerd.