The mechanic is ... interesting. You no longer have to keep track of durations, which is nice... But consider the following...
Effect lasts 1 round or more: 100% chance (it always lasts until the end of your turn)
Effect lasts 2 rounds or more: 45% chance (55% chance that you make save without bonuses)
Effect lasts 3 rounds or more: 20.25% chance (.45 * .45)
Effect lasts 4 rounds or more: ~9.1% chance ((.45)^3)
Effect lasts 5 rounds of more: ~4.1% chance ((.45)^4)
Maybe it's a nastier spell, and there's a +5 to the saving throw required... So you need 15 or higher each round.
Effect lasts 1 round or more: 100% chance (it always lasts until the end of your turn)
Effect lasts 2 rounds or more: 70% chance (30% chance that you make save without bonuses)
Effect lasts 3 rounds or more: 49% chance (.7 * .7)
Effect lasts 4 rounds or more: 34.3% chance ((.7)^3)
Effect lasts 5 rounds of more: 24% chance ((.7)^4)
Now consider what would happen if the effect was +11 to the saving throw for some reason... The effect becomes permanent. Unless there is special text in the saving throw rule for 20s. I've seen such text in the miniatures rules (20 ends all ongoing effects), but not in the prerelease handouts. I'm sure 20 is an auto-save, but still it would be a cool mechanic for things such as permanent charm persons...
Bah, I'm just deluding myself. I'd be willing to bet that 20 is an auto save.
