Note: Potential percentages of unique visitors per day highly depend on many factors! (publicity of the wiki; visitors' region(s); number/length/quality of articles; number/quality of blue wiki links; wiki project/usage type; human/bot ratio; number/quality of competing websites; reputation of the wiki; ...)
For Wikipedias(used for relatively extensive browsing) being in a range of ± 27,000 total hits per day I can say that the number of real visitors per day (those who are viewing article content, so not just 'passing by' on Main_Page/non-articles) seem to be at roughly 9 %.
For Wiktionaries(used for relatively quick lookups) being in a range of ± 350,000 total hits per day I can say that the number of real visitors per day (those who are viewing article content, so not just 'passing by' on Main_Page/non-articles) seem to be at roughly 11 %.[The wiki this was measured at sometimes seems to have extensive bot/script/download traffic!]
This was measured by a tricky way for only one of those Wikipedias and only one of those Wiktionaries I have access to, by using the logs of user:midom in combination with JavaScript/cookies [anonymous > non-invasive, in respect of the Wikimedia privacy policy]!
Note: Compare with the older Webalizer data for page requests and visits (latest average was 7 %; rather high percentage at smaller wikis (up to over 11,x %); rather small percentage at bigger wikis (down to 6,x %))!
