Going to 2.0.3 from .10 I only had two issues.Hmm, 1.0.10 appears to still be the recommended version. Can I safely update to 2.0.3? I understand I'll want to backup my world and be prepared to downgrade, but are there any known "don't do this or you'll break your world" incompatibilities?
#1 The liquids in my ex nihilo barrels all changed to other liquids. Not a big deal.
#2 I had to summon in an editable quest book to fix the glass quest as it was stuck. Maybe already having turned in 150k clear glass and >100k glass messed it up when moving to .3 drastically reduced the requirements.
So only 2 issues for me, both easily fixed. Worst case scenario you have to rollback the modpack version and restore the saves you backed up before upgrading.
If you'd like a LOT of the quests to be easier going to .3 is worth it. You might even want to go back through your quest book to look for key rewards that were changed, like the ender/monastic bees.
Speaking of recent derps, this is my latest:
Massive manual slime tree farming for blue slimes when I could have just used my autospawner for green slimes and then auto-dictionaried the output---which made the quest take about 30m.