Don't underestimate the value of the lessons you've learned in the bowels of that corporate product. Consider:

1) You have experience in a corporate environment. You know the kinds of things that terrify them, and you know the kind of experience they expect from the companies they interact with. This knowledge and perspective is incredibly valuable to any startup in the b2b space.

2) The problems you solved - while maybe specific to the corporate product - generalize well. There's a better-than-even chance you had to deal with managing data from multiple inputs, scaling and performance, build management, testing issues (even if experience in pain of not having it), product delivery, and/or user experience. These things are not as different as you might expect.

Reference: I spent many years working for a Large Bank developing in-house software before transitioning into the startup world. THe biggest problem I had faced was my complacency - somewhere along the way I gave up on pushing to do things better, and it took me a while to get that back. In that way I was fortunate that I came to work for a company that gave me the time I needed to do that.

Thanks for the words of encouragement.

I'm not totally pessimistic, I was really referring to the knowledge that doesn't translate to a new job. After 10 years and working deeply with a lot of stuff I am among the 'Do you know..?' types for questions about the inner workings of the product. That is really just baggage.

Processes, experiences probably can be reapplied elsewhere. But having read some C files from 1996 (I .. didn't work at that company at that time), reciting the product's API every evening after dinner and being intimately familiar with the current .Net code base is time invested in this job and this job only.

>> But having read some C files from 1996 (I .. didn't work at that company at that time), reciting the product's API every evening after dinner and being intimately familiar with the current .Net code base is time invested in this job and this job only.

I disagree with this, you gain something working closely with a legacy code base. After you've done it once, it becomes easier when you have to it again, although if you do it more than a few times, it gets REALLY old. I distinguished myself at my last two jobs by jumping into and becoming proficient with the legacy code in short order.