OK, here's the text from the PRD
Dilettante
What some would call dabbling you call a wide range of interests. Your breadth of knowledge offers unexpected insights in many situations.
Prerequisites: 2 ranks each in 5 different Knowledge skills.
Benefit: You gain a +2 bonus on Knowledge checks if you have 1–5 ranks in that skill. This bonus does not stack with Skill Focus. You can make untrained Knowledge checks with DCs up to 15.
Normal: You may only make untrained Knowledge checks for common knowledge (DC 10 or lower).
My question is, does the feat stop offering a bonus on the knowledge checks if you get past 5 ranks in one of the skills? My reading appears to say yes, which definitely docks the appeal of that feat.
Yes, it only gives you the bonus when you have 1-5 ranks. If you have 6 or more you get nothing.
It is a good feat if you want to know a little about everything.