I bought PTC MathCAD 7 last year - do I need to purchase MathCAD 8 if I want to upgrade?

FYI, people with active Mathcad subscriptions are entitled to both Mathcad Prime 7 and Mathcad Prime 8 and can download either or both at no additional cost.

There is no cost to upgrade; the subscription price covers that. It's been an on-going PTC research interest in understanding what prevents folks from upgrading to the latest version when it comes out. It's easier to understand that for a complicated, heavily customisable enterprise-wide product like Windchill; but that doesn't really apply as much to Mathcad and its typical customer base.

In the Mathcad Prime 8 launch webinar, I asked the product manager about Prime 7 opening Prime 8 worksheets (28:43 in the replay), and he said he's looking for customer use cases for that direction of compatibility. He said one use case is when one is working at a large company or a company that deals with other companies and if they have different versions, there ought to be a "base version" of compatibility.

It's in the established spreadsheet of customer requests, but it hasn't reached the priority level of actually being included yet since the business value isn't quite as defined as other requests being worked on for the next few releases, like a lot of the still-missing legacy Mathcad features.