Mike Morgan - Scalable PHP with APC, memcached and LVS (Part 2):
"In our journey with addons.mozilla.org (AMO) we made some interesting group decisions a year ago that we regretted later:
PEAR::DB was unnecessarily large, and Smarty is just not worth it — it confuses the issue and redoes things PHP is already good at using arbitrarily complicated syntax. Any quick run through with something like the Zend Profiler or APD will tell you how much of a dog these things can be. If you haven’t already, I highly recommend profiling your app to see where you’re losing performance — I bet it’s mostly in includes."