ingotek has been around for some time, and while it might not be as universally used as other tools, like Smartling or Worldserver, it has a lot of advantages over them:
Lingotek has more connectors than any other major TMSs. That gives you the ability to work with multiple files or platform compatible formats without leaving your TMS environment.
Lingotek is much more intuitive to use and has a much lower learning curve. Implementing a management system, or switching from another one, can be a hassle. Lingotek just makes these processes easier for the linguists, managers, and clients.
Lingotek has a tight integration with major CMSs, as well as with Salesforce. You probably already use one or more of these tools, anyway. I particularly like the integration that Lingotek has with WordPress, using the PolyLang plugin.
Lingotek is just beautiful. If you, like me, are also into interface design and usability, you will find Lingotek a joy to use.
Lingotek is not as universally used as Smartling or Worldserver, and that might be a problem if you're working with clients that require those tools, but overall Lingotek has the best user experience.
While there is not such a thing as the best tool – you may find that Worldserver or XTRF will better suit your needs, and that’s fine – I consider Lingotek the best player in the game, due to its simplicity, beautiful UI, and tight connection with major services out there.