Marketing and selling software to enterprises is the most dysfunctional cycle of decision making you will ever see in business. In almost all cases the individuals in the business who actually derive value from the technology are entirely disconnected from those who make the purchasing decisions. Many times those purchasing decisions are made based on "perceived" synergies with other software systems already owned from the same vendor, having never been vetted by the actually consumer in the business. Enterprises represent a huge market to be served by well designed/functional applications. Keep in mind that most Enterprise SW contracts have customers paying yearly maintenance charges that are 20% of the original license cost and sometimes more...
The thing to understand in selling into this market is you need to adapt your "logical" marketing and sales strategy to the way enterprises buy. I say adapt b/c you can't make or help a dysfunctional buyer behave differently. These companies like centralizing technology decisions, large multi-year commitments and have complex IT accounting considerations. You need to be aware of their existing legacy infrastructures and have a story of how you "play nice". You need to have partnerships with existing large Enterprise SW companies (IBM, HP, Microsoft, Oracle,etc) and you need to have Rolex wearing sales guys who have the connections and can get deals done - http://techcrunch.com/2010/11/13/new-enterprise-customer/
If you do all that, just moderately well, a large SW company would swoop you up really fast. They can't innovate new marketable products worth crap, all they do is buy. And although we hear about some of those acquisitions there are many, many more that don't get as much press...
However in contrast to the approach above I have been whiteness to a handfull of startup business models that have done really well at infiltrating the enterprise based on their distribution and user engagement model. Take Yammer for example, their model allowed for people in large companies to start using it (for free) without having to get any approval from their IT departments. I had a CIO friend of mine who never heard of Yammer until I mentioned and showed him where over 100 of his company employees were already active on it. Large companies have to worry about compliance, document retention, etc. His first reaction was to block it via the firewall, but then he was smart enough to see it as an opportunity to invest in a technology that had actually been proven to deliver value by people within his own company. Software or services that can get into the enterprise like a cockroach, breed and spread under the radar have a really good chance of getting a CIO's attention in a good way - it's an opportunity for them to invest in a solution that works and guarantees that their business will get value since its already been proven on an small scale.