PHP vs ruby is not like going from java to ruby. You may see productivity gains. However, PHP is so well established you may even save time by taking advantage

PHP vs ruby is not like going from java to ruby. You may see productivity gains. However, PHP is so well established you may even save time by taking advantage of all the open source code written. PHP has done wonders for the devs at facebook and digg. I feel the need for "nerd cred" is too high these days. Using older tech that has a proven track record is still a good idea. Your start-up may not be the cool kid on the block but once you're making money nobody cares. I do use python and django myself and LOVE IT! Can add that to your list?