All systems had a beginning somewhere. Some degree of diversification is not necessarily a negative. But don't expect too much in-depth information, as a vendor will be reluctant to disclose too much about their products publicly. Ask for some recent and back copies and read them carefully. You can tell a lot about vendors and relationships with clients from their newsletters.
Brochures are a less reliable information source as they are essentially a marketing tool.
Be aware that vendors will sometimes include in their brochures functionality which is still in the planning or development stage and therefore not available at this point in time. Check this out. Ask what the developer's plans for the system are for the next couple of years. Bear in mind however, that software developers are often compelled to reassess their plans in the light of technological and market trends, economic issues, and also as a result of pressure from clients for specific functionality. Examine very carefully the support and maintenance arrangements being offered by the vendor.