I purchased the 1750 from Seidio last week. I turned off the phone and inserted the the battery. It came from Seidio showing 2 bars (out of 5 on the meter in the off state). It charged up to 5 bars in about 3hrs, and I then left it charging for about 8 more (Seidio recommends 2-3 hrs after showing full, but I wanted to make sure it was full the first time around). On this first charge, I'm currently at 2 Days, 17 Hours and 30 Minutes of use, and have 7% remaining. I'm going to let it die so the calibration software gets a complete reading once, then partial charge from ~25-50% from now on (supposed best practice with Li-Ion in regards to battery life cycle. 100% depletion nets you 500 recharges, less gets you ~1500-2500)
How to Prolong Lithium-based Batteries – Battery University
So far, this battery is beating the stock one (on my phone) by almost a day, and it's supposed to improve after 5-6 charge cycles. I'm happy with the purchase.