There is no customs fee for the US, right?

I'm glad I don't live in UK!

According to bitcoinwisdom.com calculator, the antminer s1's ROI in about 90 days.

Is this about correct? More? Less?

Not sure... was expecting a good drop as BTC price has jumped 25$ from what yesterday price was set at.

Have you guys looked at what the actual power savings are in comparison to the added cost of a >bronze supply?  For almost every attempt I've made to justify higher efficiency supplies the savings just never make it worth while.

Ordered 3/07
shipped 3/10
Arriving today 3/12

I am in Toronto near the airport.

Another option is to underclock and run 4 off a single PSU.

Run the math: you may find that it makes more economical sense to save $100-$200 on additional PSUs, rather than getting an extra 10-15% hashrate by overclocking. Everyone's situation is different.

I run 4@325MHz on an EVGA 1300G2, and another 4@325MHz on a Seasonic X-1250. These combinations use ~1400W at the wall (@120V) as measured with a Kill-A-Watt meter, which is fine for those PSUs and is within the continuous rated limit (80% of 15A/120V: 12A or 1440W) of a single 15A/120V household circuit.

Some other combinations I run: 2@350MHz (stock) on a Corsair HX750, 2@350MHz on a Corsair AX760, and 2@375MHz (overclocked) on a spare Seasonic X-1250 (which is overkill for 2 Ants).

I think the power costs will be much less than that.
400 watts x 24 hrs day1000 = 9.6 KWH a day times $.10 x 90 days=$86.40

Assuming no dead chips, you can expect roughly:

325MHz: 167 GH/s
350MHz: 179 GH/s
375MHz: 192 GH/s

These numbers will vary a bit across hardware and firmware revisions. In other words, YMMV. The difference in reported temperatures between the 3 speed levels is minimal from what I have seen; perhaps 1 degree at most. But since 325MHz Ants generate 45W less heat than 375MHz Ants, the fans on the underclocked Ants run slower (and quieter).

And ofcourse save on electricity bills and psu ... makes sense