Same here. Logged close to two full day's worth of ships and colonization (I colonized two new planets, built four new outposts) - in fact my two Probes explored almost 75% of the grid prior to the downtime. All reverted to the last saved state (I suspect) of my original planet and outposts (and only 40% grid explored) after the Nisaha server downtime happened. I've given up on rebuilding those lost fleets as it's too exhausting to monitor and rebuild.
My feel is that server saves need to be almost asynchronous to avoid major disappointments especially to the more active players. Rollbacks are fine, but a notice and apology for what we've spent time building and lost would be better. I'm not renewing my subs for now.