It is okay to do so, but generally not recommended for several reasons.
One, many sellers may simply not believe you're serious if you're not looking with an agent. And in the market currently, many homes sell so quickly that when you view a home you KNOW you are interested in, you want to look as serious as possible.
Secondly, an agent is familiar with the area, with homes, and has a vast array of knowledge and resources which the typical homebuyer does not. An agent, ideally, should be able to direct you to potential problem areas while also espousing the benefits of the property which you may not know or know to look for.
If you intend, on the other hand, just to take a look and then re-schedule another time to bring the agent in, there's certainly no issue with that. :)
If you've got any other questions, please feel free to contact me here on Trulia or via my website at http://www.nashvillespropertysearch.com