It’s hard to believe that Google launched Gmail in beta in 2004 and publicly just a few years ago in 2007. As of the end of 2010, nearly 200 million people across the globe were active monthly users of the free email service. If you have a Gmail account, you also have Google Chat (and if you’re a PC user, the ability to download the desktop app, Google Talk). And if you’re not using it as your go-to messenger yet, here are ten reasons you need to:

1. Voice and Video Chat are included.

First and foremost, Google Chat is no longer restricted to just text. In August 2010 Google introduced Google Voice and Google Video within Chat, allowing you to talk for real and even face-to-face with video through the service. All you need to do is download the plugin and have a video camera, and you’ll be ready to chat with video and voice in a matter of seconds. If the contact you want to call has a camera icon next to their name you’ll know they can also make a Voice or Video call. If they don’t, send them right along to this page to learn how to get setup.

2. It’s free – including Voice and Video, and even internationally.

No matter where you are in the world, all you need is an Internet connection to use Google Chat. Whether you’re paying for that Internet at your home, at work or at an Internet café, there are no other costs associated with Google Chat. And that includes Voice and Video chat, even internationally. Kiss your Skype credits goodbye, and talk for free with video and voice thanks to Google.

3. Enjoy in-line media viewing.

How many times a week does someone chat you, “Check out this video”? Google Chat allows you to watch videos sent your way in-line within your chat box, and without having to open a new webpage. Google Chat recognizes any YouTube or Google Video URL, allowing you to check out that video in one click and without reloading another page. (Chat in iGoogle and orkut does not support in-line media, however.)

4. Control your accessibility and status.

Google makes it easy for you to control who sees you online on Google Chat. You can set custom status messages, like your away message back in the good ol’ days of AIM, and choose from the preset statuses Available (green light, which turns orange if your computer sits idle), Busy (red light), and even go Invisible so none of your contacts can see that you are online. Really want to disconnect? You can of course sign out of Google Chat, too.

5. Access Chat beyond Gmail.

Part of what makes Google Chat so convenient is that it all happens right within your Gmail, which you likely sit in or at least frequent several times a day. But what many don’t realize is that you can also access Google Chat outside of Gmail in iGoogle (personalized Google homepage), orkut (Google’s social network), and through the Google Talk client. Google Talk software is available only for PC owners, and is a downloadable desktop app similar to the Skype app. Another big perk for accessing Chat in any of these places is that you can also transfer files to contacts (unfortunately right now you cannot send files through Chat in your Gmail).

6. Chat histories are treated like an email.

Google by default saves all your Chat histories, allowing you to search for anything within them in a jiffy. Google treats the Chat as an email, meaning it’s searchable right from your mailbox. Not confortable having these convo’s backed up to your email? You can “Go off the record” in any given chat by clicking the Actions dropdown, or change your default settings to never saving these chats. Whatever you prefer, Google puts the control at your fingertips.

7. Group Chat is limitless in number.

Group chat allows you to set up your own chat room with a bunch of friends, family or colleagues. Google makes it easy to invite people by connecting with your address book, meaning all you need to do is type the name of the contact you want to invite. Each person invited into the chat room can invite others, too, and there are no limits on the number in the chatroom.

8. AIM integration makes switching easy.

I’m always caught off guard when someone asks me for my AIM screen name, but there are undoubtedly still people using the service given those asks. Google allows you to integrate with AIM, pulling your screen name and contacts right within your Google Chat list of contacts. This makes switching away from AIM and into the benefits of Google Chat a breeze.

9. Automatic contact inviting and sorting gets you up and running quickly.

With all those emails flying in and out of your inbox, it’s safe to say Google knows a thing or two about the people you communicate with most often. You can actively invite people to chat with you and see when you are online, but Google also, by default, shows you as available to the contacts you communicate with most frequently (yes, you can change this setting of course). Google also uses this knowledge to sort your contact list by those you communicate with most frequently (and yes, you also have the option of changing this to be sorted alphabetically).

10. Great for both emoticon lovers and haters.

We just had to include this as the last point on the list. Google Chat comes with four different sets of emoticons, from your run-of-the-mill basic smiley faces, to more colorful and animated ones. Have fun with these, and if you really are a hater, head right into your settings to turn emoticons off for good and avoid ever having an animated smiley sent your way!

What other features make Google Chat your go-to? Let us know in the comments!