I have had the Anker 1900mah in my phone for the last 36 hours or so...it's at 56%. My stock battery would have certainly been below 20% by now.
The only trouble is, I ordered it with an RND dock/battery charger...the Anker battery is slightly thicker than the HTC battery, and while it fits fine in the phone, it didn't fit well in the docking station's battery slot. I had to force it in. Because of this (and because of the crappy design on the docking station), the "tension tab" that's supposed to hold the battery in the slot and keep tension against the charging pins broke, so I haven't yet been able to tell if it's making contact. Worst case scenario, I'll have to install the 2nd battery in the phone in order to charge it.
But yeah...long story short...the Anker works better than expected.