Yes it's worth it. Once you get the hang of which ever framework you choose, you'll easily be able to maintain neat code, site structure, and everything else that is usually annoying and monotonous to work with. However, others might argue that using a framework is not as good as hand-coding everything, which in my opinion is a ridiculous argument.
There is also a worry of overhead to some people, but that is also something that shouldn't be worried about because there are very small and very efficient frameworks out there.
There will be a learning curve for each framework you try, but it'll be worth it in the end. So, if you've been coding for a couple of years like you say you've been and you are considering a framework for your next project, I'd say look into it. It'll be a learning experience and probably fun too.
If you happen upon CodeIgniter, check out the "CodeIgniter from Scratch" videos over at
http://net.tutsplus.com/?s=CodeIgniter+from+scratchI also recommend trying Yii (beacuse it's what I'm learning at the moment) and Kohana (because I've heard/read it is very good).
Good luck.