It's a valid job choice and it can pay well, but you'll find yourself losing control of your career options. Once you've got 5 years on Huge Vendor Suite X (HVSX), you're going to find that it pays well but there are comparatively few shops using it and that your transferable skills aren't easily sold to companies that don't also use HVSX. You'll find even incremental career advances within the HVSX field require direction competition with your coworkers or even relocation to cities large enough to house other HVSX-friendly corporate headquarters.
General-purpose development (Java, .NET, PHP, Python, Ruby, etc.) is much more broadly applicable and the skills are likely to be transferable to other cool jobs right here in your town. You'll have to work a bit harder on framing yourself though, compared to just submitting a bog standard "HVSX Practitioner Level 2" resume to the tiny list of companies who would even want to hire a HVSXPL2.
Personally I have recently transitioned away from 7 years of Fortune 1000 enterprise business intelligence into consulting Ruby development. I am learning quickly and I now feel much less subservient to the market trends associated with the enterprise BI stacks I've used in the past. Along with this, moving from enterprise IT to dev consulting means that I work in an organization that counts the fruits of my labor as revenues rather than overhead. Things can be a lot easier on you when you're not an expense to be minimized.