My models 1500 Watts and smaller use the Castle Creations 10 Amp uBEC. These uBEC's have been flawless over about 5 years. I've got 10 of them in various electric models.
As for my giant scale models, 2500 and 3000 Watts, again, they use the Castle Creations 10 Amp uBEC, with the uBEC connected to the "Center" of a 10S and 12S battery packs. Added to the uBEC is a two cell 2300 Mah A123 battery pack as a backup unit.
The two cell A123's are isolated from the uBEC with two series 10 Amp Silicon Diodes, located in series with the A123 battery pack red lead. This drops the output voltage of the A123 pack to about 5.6 Volts DC, below the set point of 6.50 Volts DC coming from the CC uBEC. This scheme has a battery undervoltage alarm with a little 8 pin PicChip microcontroller that measures the receiver voltage about 4000 times per second. If the voltage EVER drops below 6.0 Volts DC, the under voltage alarm shows just how low the battery voltage dropped. After over 500 flights in two giant scale models, those under voltage alarms have never gone off with the Castle Creations uBEC.
I did have an undervoltage alarm indication after a flight on a Common Sense switching BEC on the Giant Big Stick model. My monitor showed that the Common Sense output had dropped to 5.8 Volts DC on one flight. That Common Sense unit was replaced with the Castle Creations uBEC, and no more problems were noted.
The maximum peak current pulled by the Giant Big Sticks seven Hitec 645MG servos has been measured at 14 Amps, on my $$$$ Fluke 87V digital multimeter, with its millisecond measuring peak hold feature.
After some 100 flights, it only takes about 150 or 200 Mah to "Top Off" the A123 battery packs. This is due to operating the receiver only from the A123 packs during testing, or while powering everything up.
This thread shows how the CC uBEC and two cell A123 backup battery was wired up: