I've tried similar decks pre-upgrade and was not impressed; while you can get a lot of small creatures out fast, their un-upped damage output just isn't enough to kill most decks before they get their winning strategy into play. You're pretty vulnerable to creature control too, especially from repeatable sources; otyughs see all your frogs and cockatrices and yell "BUFFET TIME!" Ultimately I found that success hinged entirely on the dragons, and since every color has dragons I figured I'd be better off going for a color that has better abilities to contribute.
The upgrade for frogs is a very good one and might push it into competitive viability, but I don't have the firsthand experience to say for sure--most of the losses I racked up with mono-life before the upgrade pushed the enemy health low enough that I might have scored a kill with 5-damage frogs instead of 3, but those were against un-upgraded decks as well; similarly upgraded decks might have new answers for your new and improved frogs.
Bonus points for originality, to be sure--the life element doesn't get a lot of love, so it's always good to see someone eking some success out of it. I'm just not sure it's quite there yet in terms of the card available to it, though.
