Wordpress.com is one of the most powerful CMS available. It has many plus points but also lacks in some areas:
There is not much customization freedom. You won’t be able to access the code, and if you are a developer that is a big no.
I didn’t like the .wordpress.com at the end of every domain. In order to use my own domain I had to pay a huge yearly fee. I couldn’t bear it.
Wordpress starts showing ads automatically on my blog, even If they weren’t paying me.
Final Verdict: Best for those who do not want to pay and only looking for fun.