Odd question and vague question.
However, php is very robust can do virtually everyting you can do with perl and asp...but much quicker development.
As far as speed...php4 is blazing quick and can handle virtually any amount of traffic. You have to remember that any server has a limit how much traffic it can handle.
If your e-bay or amazon your not using just one server...but dozens. PHP makes as effecient use of server resources and is as fast you could ever want for the vast majority of applications you'd be using it for.
Because php parses rapidly it actuall free up processor time better than other technologies such as jsp. Why jsp even exists is a mystery to me!
As far as lacking features - not likely. I've been using php for over a year and I haven's found anything that can't be done with it...from e-commerce, database driven sites and for auto-graphic manipulation functions you can't find anything better than the gd and php combo.
There are thousands of large companies that rely on php for virtually all programming needs...you can't argue with numbers (well unless your talking about MS).