I'ved tried 3157 LED bulbs similar to these ones:
http://cgi.ebay.com.au/3156-3157-Sup...QQcmdZViewItem
I bought these in white colour and was quite dissapointed because they weren't as bright as the stock incandescent 3157s. My car is a gen4.5 camry btw. And yes, if you use them as the signal bulbs they will blink superfast due to having less resistance than normal incandescent bulbs. So it's best to leave them in the brake lights.
I'm not saying the ones you're looking at are bad, I'm just letting you know my own experience with LED bulbs from eBay.