1) JMP and SAS can be complimentary to one another, or they can stand alone. There is a fair bit of overlap in the capabilities of JMP and SAS. I would not call JMP a niche product; JMP is a powerful statistical package.
2) JMP now has a programming language, so it can be used in "point-and-click" mode, or via programming commands; however I dislike the programming language in JMP and avoid using it as much as possible. SAS can be used in programming mode, or there are full-screen GUI interfaces that can be used.
3) SAS has more modeling algorithms available. JMP can handle some very large data sets, I have not yet reached a limit. Regarding "custom" models, JMP can fit some "custom" models, don't really know what you mean. I don't use .NET so I can't answer those questions.
Message was edited by: Paige