I've been using underscore_case for about 2 years and I recently switched to camelCase because of the new job (been using the later one for about 2 months and I still think underscore_case is better suited for large projects where there are alot of programmers involved, mainly because the code is easier to read).

Now everybody at work uses camelCase because (so they say) the code looks more elegant .

What are you're thoughts about camelCase or underscore_case

p.s. please excuse my bad english

Edit

Some update first: 


platform used is PHP (but I'm not expecting strict PHP platform related answers , anybody can share their thoughts on which would be the best to use , that's why I came here in the first place)
I use camelCase just as everibody else in the team (just as most of you recomend)
we use Zend Framework which also recommends camelCase


Some examples (related to PHP) :


Codeigniter framework recommends underscore_case , and honestly the code is easier to read .
ZF recomends camelCase and I'm not the only one who thinks ZF code is a tad harder to follow through.


So my question would be rephrased:


  Let's take a case where you have the platform Foo which doesn't recommend any naming conventions and it's the team leader's choice to pick one. You are that team leader, why would you pick camelCase or why underscore_case? 


p.s. thanks everybody for the prompt answers so far

I think you should use naming convention adopted by your platform. underscore_case will look weird in C# code, as camelCase in Ruby =)