Setup is quite simple: install the Android app, grant it access to the Google account tied to your phone, then install the Chrome extension and give it permission to the same account in your web browser.
MightyText will grab your phone's contacts and sync them with the web, so everything will be set up automatically. When you load Gmail, you'll notice a "compose SMS" button right below the regular "compose" button for email. Clicking it opens a panel much like Google's tasks or Hangouts panel. Enter a recipient, compose your text, and send it. Simple.
You'll also notice links below the "inbox" link in Gmail's sidebar- one for texts, and one for photos and videos. Clicking on either will show you an interface not unlike the texting app on your phone, where you can select recent conversations and reply instant-messenging style.
The extension even adds a battery meter for your phone in the upper right corner of the Gmail window.
You don't need the Chrome extension to use MightyText- there is a web app available on the main page. Most will probably use the Gmail interface, though, since it's one less tab to keep open, and most of us already keep Gmail open all day.
MightyText has a few other tricks up its sleeve, too, like a dialer that will call your phone and connect you to the number entered automatically. Most of the extras are reserved for the pro version, though, which will set you back four bucks a month, or thirty per year. That'll get you features like scheduling texts for later, organizing your contacts into lists, themes, number blocking, and quite a bit more.
For those that don't use Google Voice, MightyText is a godsend for any Android user who spends a significant amount of time in a web browser. In fact, it's a powerful alternative to Google Voice, and even offers features that Voice doesn't. It's not enough to make me switch—one phone number for life and voice transcription are too good to give up—but I'd be lying if I said I wasn't tempted. MightyText is a solid platform that fills a number of needs.