At WordPress.Com, you have to use the themes provided. And the last time I checked, you can’t use Thesis. You can’t add advertising. You have to purchase the ability to use your own CSS. If you want absolute freedom, get WordPress from .Org. Click the “How to Begin” section above for more information. This site uses WordPress.Org, as do all my other sites. NOTE: even if you pay for hosting at WordPress.Com, you will not have the freedom offered by WordPress.Org.
WordPress provides updates to the platform on a fairly regular basis. New features are added and new security measures are put in place from time to time. Personally, I tend NOT to jump at the first mention of an update being available. I try to see if others are having any problems and how they solved them, so that I can be forewarned. However, most updates are tried and true. It’s just me, you know – I’ve got issues.
There are many, many themes available. A lot of them are free and some you have to pay for. The ones you have to pay for are usually called “Premium Themes.” Prices can range from $10 to $500+ depending on the functionality you want. Since I’ve chosen to go with Thesis, and have the Developer’s option, I don’t search for themes much these days. When I did, I chose to get them directly from the WordPress.Org site. Those themes are generally approved by the WordPress organization. Many are very stylish and work very well. There are some well established sites that offer free WordPress Themes. I’ve used some on occasion.
The same goes for plugins. WordPress.Com does not allow users to use plugins. You can use them with WordPress.Org. I get mine directly from the WordPress.Org site. The advantage is that, again, most are approved beforehand, and there are forums that address issues with their functionality. Honestly though, I try not to use many plugins. I tend to use as few as possible.
And probably one of the most important tips I can give you is: WordPress.Com and WordPress.Org are open source platforms, meaning they are FREE. Do not pay for WordPress. (themes are different). Generous people from around the world have made this platform available to all of us at no charge. Plus, when you visit the WordPress forums, be nice. Most of the responders there are volunteers, unpaid volunteers. Ask for help politely and make no demands. Maybe one day, when you become a WordPress pro, you can pay it forward by helping someone.
For more information on WordPress.Com and WordPress.Org, check this link: Differences Between the Two WordPress Platforms.