Absolutely you should try one. If nothing else, it will greatly improve your OOP knowledge. I’d suggest reading the documentation or getting started guide for Symfony (link in my signature). It is well documented and an extremely good framework.
I believe they’re all good frameworks, but I’ve only used symfony to any extent. Agree with AlienDev, go through their tutorials/docs to get an idea. Another one that seems to be gaining popularity is Yii (not done more than glanced at it though).
Sorry, I cannot assess your skills, so don’t be offended, but if you don’t have some already, gain some basic OOP programming knowledge or it may all seem like gibberish to you and you will lose twice as much time wondering how things work like voodoo-magic.
If you have some OOP experience though, I would definitely suggest learning one of these frameworks. Personally, I think the best frameworks around are Zend Framework and Symfony (in no specific order) so any of those two would be great choice. No offense to CodeIgniter but supporting PHP4 these days just doesn’t sound right.