Here are some methods for gathering user feedback on a GUI:

1. User interviews: One-on-one interviews to gather in-depth feedback.

2. Surveys and questionnaires: Online or offline questionnaires to collect feedback from a larger user base.

3. Usability testing: Observing users interacting with the GUI to identify pain points.

4. A/B testing: Comparing two versions of the GUI to determine which one performs better.

5. Heuristic evaluation: Expert review of the GUI against established usability principles.

6. Contextual inquiry: Observing users in their natural environment to understand their needs.

7. Focus groups: Group discussions to gather feedback and opinions.

8. Online analytics tools: Tools like Google Analytics to track user behavior.

9. Customer support feedback: Analyzing feedback from customer support channels.

10. User testing labs: Controlled environments for testing and gathering feedback.

11. Remote usability testing: Testing with users in their own environment.

12. Feedback forms and forums: Online forms and forums for users to provide feedback.

13. Social media monitoring: Monitoring social media for user feedback and sentiment.

14. Competitor analysis: Analyzing user feedback on competitors' GUIs.

15. Accessibility testing: Testing with users with disabilities to ensure inclusivity.

These methods help gather valuable feedback to improve the GUI's usability, user experience, and overall performance.