Evaluating and selecting a new line-of-business technology can be daunting, and it's easy to lose focus on what matters once you have a panel of sales guys coming at you. What you need to remember is that you aren't just buying technology. You're buying a relationship.
Vendors are great at demos. They're great at finding your pain points, latching onto the things that align, and glossing over the things that don't. Most people aren't equipped to see past that.
If this is a key business application, you need the technology to fit, but you also have to understand who's behind it. Who supports you after the sale? What happens when something breaks? What happens when, not if, something doesn't work the way they said it would? What's the total cost of ownership beyond the monthly or annual fee? What do renewals look like? What does an exit look like? Get relevant references from your industry and scale. Better yet, find some customers they didn't give you and call them for the real story.
I've been in a situation where my primary line-of-business app mostly worked fine, but the vendor behind it was a black hole. It's not a good position to be in.
The killer question is often this: tell me about a customer who left, and why. How they answer can tell you a lot, especially if they try to claim they don't lose customers.
A bad technology decision is expensive twice. Once when you buy it, and again when you have to undo it. Take the right steps up front so you can avoid the second one.