[mxuribe]

As others have posted, involving (potential) users and key decision makers - such as sales/marketing, etc. - is ALWAYS a good idea. The key here is that you don't want to pose open-ended questions, because that doesn't help. You need to corral these folks. Asking a sales/marketing person what they think of this platform or that in such a generic fashion, will no doubt lead to general comments such as "oh, it seems to be a user friendly system" (according to or against what measurement?)...or comments like, the "UI and/or buttons seem good", etc. Nope. Instead, what you want is to very concisely drive these stakeholders down a very specific path to extract very specific feedback, in a quantifiable manner from them. You want feedback that is actionable when making your decisions. To be able to think of ways of corralling these folks is a skill; don't be fooled into thinking this is so easy. But you should definitely give it a try. Good luck!