Don't know what you have in mind for "other potential usefulness" with hero souls, but here's an idea: Currency for special Upgrades, like lowering level up costs or raising the soul cap itself. Of course the payoff would have to be worth the trade in of the buffs the souls themselves give.
"The trick is getting 3k+ on the first day" Am I even playing the same game?! Its barely possible to get $250 on the first day, how the hell can you get 3k+??
I got day 14 defeated at 2:13 but the delay between all enemies defeated and the level ending is so bad it pushed it to 2:15, not giving me the in game achievement. I declare SHENANIGANS!
Ok I made a thread in forums about the problem due to the quest http://www.kongregate.com/forums/7-technical-support/topics/167235-best-of-2007-quest-uncompletable?page=1#posts-3642211
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