Old School Essentials (OSE) for the first time last night (as a player) through Roll20. Playing The Bonesmith the Lawful Cleric from the OSE Rogues Gallery. Setting is dark and at least partially weird. Using ascending AC.
Migrated from Astonishing Swordsmen & Sorcerers of Hyperborea. OSE is more to my taste than AS&SH, at least in terms of rules and book layout/formatting.
The rules work perfectly and naturally. Effortlessly. Almost no need to reference the books once character sheets were ready (a few minutes' work). Only time we (players) looked into the book was to check how the Sleep spell works in this specific ruleset (it changes slightly between OSR games).
Fought some bandits and some wolves. Combat is fast and brutal. Though we spent most of the session role-playing and exploring, with the Referee rolling a few dice here and there (for random encounters, as far as I recall).
All in all, one of the best OSR rulesets I played!