Add one more happy (and thus throughly frustrated) user here.
Like alot of others, I bought the Seidio 1750 at full price, because it seemed like it would be better than the 1300 stock. Admittedly, i never tried the stock, but the 1750 sure has heck left me wanting. The phone can idle for two days, but any good load on it, and it is shot within a couple of hours. Do something like an Angry Birds session, and it is painfully bad.
Upon getting the new battery, the first thing i can tell is that the construction is better. Seidio, the cell is just held by the black label wrapper, and not attached to the plastic frame at all. On the ChiChi, the entire battery is fully case, and feels more sturdy. I know it doesn't really matter IN the phone, but even before use, it feels like a MUCH better battery.
It will take me a couple of uses to really tell where i am in stats, but i KNOW it is better already. I have always pump charged my batteries, but this one stays at 100/high 90s for much longer than the 1750 ever has. Last night once on the charger, the phone had been unplugged for about 18 hours, with around 3 hours of on-time, and had 40% left. Keep in mind, at least half of that half time was playing Angry Birds, which is killer on a battery.
What frustrates me, is how much i paid for Seidio, and how little in comparison i actually got. Even if the ChiChi battery is only as good as the Seidio (which it is better), the $15 is much more reasonable. Seidio really has a knack for ripping off.. i really hope that HTC Express gets more of their potential business in the future...