What are some alternatives?
productboard - Beautiful and powerful product management.
ProdPad - ProdPad helps your team gather ideas, surface the best ones and turn them into product specs, and then put it all on a product roadmap.
Viima - Viima's mission is to allow companies to build what their customer wants, or in turn to fail faster with minimal wasted effort
Aha - Aha! is the new way to create visual product roadmaps. Web-based product management tools and roadmapping software for agile product managers.
Crowdicity - Idea management software for smart organizations.
Arbor - Easily manage product development