I'm disappointed by the upgrade kit. Since you're replacing the boards, you're only getting ~273 additional GH/s for .46 BTC. Yes, it will be more efficient, so there's that.
I agree. An undervolted S1 getting 140 gh/s is closer in power efficiency to the S3, but the net pickup of an upgrade kit is only 313 gh/s...for .46 BTC 37 days out. I'll pass.