Three words: Focus on Technology.
But does “being cool and up-to-date” really matter when it comes to “serious” (and with “serious”, I mean “professional”) development?
For example, I have collected a lot of experience in Windows PowerShell in an enterprise project. In a subsequent enterprise project, a colleague once laughed at me for using PowerShell instead of Perl for a simple scripting task. In my opinion, that situation is distinctive for the mindset that many tech-guys carry around. They focus on technologies, not on the business value that is added by a technology. Certainly, I could have used a Perl script instead of a lame bunch of PowerShell (in fact, PowerShell ain’t that lame). Perl (as a classic hacker language) is cool, but I have not as much experience with it as I have with PowerShell. In fact, writing cool code is not essential in professional development. Instead, efficently writing working code is what really matters in enterprise/start up projects.
Additionally, when it comes to trendy technologies like e.g. Ruby on Rails, people tend to see it as more advanced (compared to old-fashioned Java) because it fits current web development needs by design. Moreover, start ups have developed a serious fetish about using fancy new technologies.
But people forget that it takes a lot of time to master a new technology (and time == money), as well as they forget about the potential downsides of recent implementations when it comes to e.g. performance or scalability. Java EE may be boring and may not fit many modern problems by design. But its implementation is reliable because it has proven itself in countless enterprise projects. And there are many people out there who have advanced skills in Java EE development. Good luck trying to form a team of real Rails experts (and not some “I-once-build-an-Hello-World-REST-API” experts).
What I’m trying to say is: When you can create business value with a technology (especially in Start Ups), don’t look around for fancy new technologies promising to be a perfect fit for your use case. Instead, rather focus on basic, well-documented technologies (even if they sound boring), that allow you to create working software for your essential business needs.