I don't have much in terms of hard data unfortunately. My site is very new, so measuring the AEO impact isn't really possible yet (no baseline to compare against). I am, however, collecting analytics on whether various routes are being hit (e.g. llms.txt and .md routes), as well as the frequency of various AI user agents, so I can do a follow-up post once I have some more data.
Based on my experiments (across hundreds of thousands of LLM chats) llms.txt does not have any measurable impact in the vast majority of scenarios.