Whether you have a domain or not, unless there is something in-between, people will still be able to get your IP. Who exactly are you planning on giving your IP? Just a few friends, or broadcasting it all over the internet? If it's just a few friends, then I don't see why not.
It's not really safe to tell everyone your IP, and you could suffer from attempted hacking/ddos attacks, which ain't fun to deal with.
Remember though, unless you're paying for a static IP, your IP will change from time to time. You can avert this by using a free dynamic DNS service (normally involves having a little program running on your computer that will update your IP accordingly). They normally let you do this with a free domain, so that means you wont...