Unfortunately, the industry we provide a service to is mired in local authority politics, so I can't disclose here. I'd like to be able to say "fuck, that is ridiculous" without someone picking up on it someday and killing my business as a result. We're proud of the product but the industry itself is very cutthroat with only a few players. It was hard enough to carve out the market we have. So, this is my personal account. That being said, it's a great market for some of the same reasons. Our current contracts are 8-10 years (but it takes a lot of blood, sweat, and tears to get them.)
Having said all that, I still disagree with your Solaris vs. open source argument in principal. You don't have to have a huge amount of customers to be doing well to me. If 95% of the people are using an open source product but you still have 5% clinging to you because they love it and you're profitable...is it really so terrible?
Of course, if you build a business, you want to be mutable anyway. You can't just sit around hoping product X will feed you and your employees without some sort of proactive business development. As part of that, you always have to be prepared for someone smarter and more agile. You play to your strengths. If you have market share, you leverage it. If you have agility, you leverage that instead.
Edit - One of the things that doesn't get discussed around here often enough, is the ability to form and execute as proper business. Your product is not (or more accurately perhaps, should not necessarily be) the entire definition of your business. Any business that expects to be around in the future must generate income. Competition is always going to be there in one form or another. If that competition happens to be people who like to work for free making open source products, it could be a mountain to climb to compete directly. The business may have to adapt in other ways.
I'll give an example of that. Everyone in our industry used to provide an embedded software component that required an OS that had a license associated with it. One of our competitors pitched an idea to build the same software using Linux. It very likely could have crippled us had they managed to deliver something at a much lower cost. So, we went through negotiations and tried to acquire them. Those negotiations failed but we realized that they really weren't close to that open source solution at all. We jumped at the chance to develop our own open source product and it is now in pilot locations. Nobody else in the industry has even blinked and we can suddenly cut some really outrageous costs out of our equation.
So, the beauty of open source, is that it's open to everyone.