This post contributes some thoughts to the "concurrent users limitation":
In the Sitefinity marketing materials, benefits to Business Users are always specifically identified. I applaud Sitefinity for realizing this, and not following suit with a lot of other companies that simply provide a long list of features. Of the highlighted benefits is "Perform your everyday tasks easier". In my view, this value statement is undone by the concurrent user limitations, because it makes it harder for business users to perform their everyday tasks -- not easier. The limitation means that sometimes a business user can't get their task completed; that they have to find a "Sitefinity administrator" for assistance or come back later and try again, or they can't post of blog entry for a nonsensical reason (from the perspective of the business user).
I can see in some organizations that the only aspect of Sitefinity that will be remembered by business users is that it's the "tool that they can't always get into it". Every other wonderful feature will never get a mention if they hit this issue more than once or twice.
For some organizations, it may never be an issue. For others, it becomes an instant deal-breaker. The problem is that the number of concurrent users needed by an organization is not solely related to the organization size / financial resources; it is also the structure and behavior of the organization that is big factor in the level of concurrency that is needed.
With the exception of the concurrent user limitations, I like the approach taken with offering multiple editions of Sitefinity. It caters effectively to hobbyists through large enterprises, imposing practical limitations on the amount of content in the lower editions, and providing more advanced capabilities exclusively in the higher editions.
I'm not trying to be a "second guesser" on every decision that Telerik makes. They've put a tremendous amount of effort into creating a market leading product, and I'm sure that they've done plenty of research into how it should be marketed. BUT, I would like to make the supposition that simply removing the concurrent users limitations on the Standard edition and up would actually increase total Sitefinity revenue in the long-term rather than decrease it. Why? -- because although there may be fewer Enterprise licenses, the adoption rate isn't hindered by this pre-purchase and post-purchase customer satisfaction issue. That seems like a win-win for everybody, doesn't it?