Sometimes a pickup just isn't right for the guitar or the user
This is what it comes down to. A good sound is a good pairing of pickup and guitar with player. It can all be shite, even if every on-paper indication say that it will work, and any given player may dislike it even if anecdotal reports suggest the opposite. Its just how that particular combination pans out; it doesnt mean to say that any given part of it is bad, its not the pickup or the guitars (or the players) 'fault'; they just dont work together.
I dont think 'you didnt play it enough' is at all appropriate. You cant just assume that if someone says something unfavourable about something you like that their assessment is half-arsed. Sometimes more exposure can change your mind as you find new things about a bit of kit, sometimes months of exposure wont alter the impression you got from the first 5 notes you played.
Its also quite telling to me that you very, very, VERY rarely see someone saying they like something met with "You didnt play it enough, in a few weeks you'll realise that its cr@p!'. Why should it have to work that way the other way around?
Personally I think 24 minutes is enough to know if you like a pickup or not. Normally more like 2.4 minutes, for whatever its primary intended style or funciton is (assessing versatility should take a bit longer!). It may change as you try to make it do different things (change tuning, put in different guitars, use with different amps and the rest of it, which will unfold over months) but if its a familiar guitar through a familiar setup, I dont see a problem with a quick assessment personally.
The only exceptions are where your initial impressions are not black or white; if youre ambivelent, it may take time for an opinion to crystalise.
Edit: Bottom line; if someone says 'I dont like it' you literally CANT say 'youre wrong'. For any reason. They dont like it. Case closed. Maybe a different experience (in this case perhaps a different guitar) would change or augment the opinion, but according to slartys eperience so far, he doesnt like it. No one should have a problem with this imo
Edit 2: Ok, you CAN *say* "Youre wrong", but you'd be wrong to!