I'm pretty disappointed with google sheet at the moment. I built some mildly complex spreadsheets for time tracking, nutrition, planning and such. They worked fine a year ago but I have experienced a massive drop in performance over the past few months. They take a minute to open and awfully slow to update calculations and no longer work reliably offline either. This is on an quad core desktop ffs.

This will kill cloud office apps if what works today doesn't work tomorrow. Cloud should not mean total loss of control of the version of the application. Something like gdocs should be offering frozen past versions of the app to avoid this type of thing being possible. Its not like frozen versions would actually add any maintenance cost to google.

These sheets are small and just have a few array forumulae. Nothing excel 20 years would have broken a sweat over.