They probably frequently lead to competitive benefits (and increased market share / revenue) for the acquirer, but the discontinuation of products presumably leads to lost time, effort, and potentially money as the former customers of the product look for alternatives (in a diminished market).
I'll beat my usual drum and mention that free and open source software can mitigate some of the risks (but not, for example, support availability) for a software-based product, similar to having an agreed source-code escrow provision with a vendor.