Trim tabs?
 

Yes or no? Mechanical or hydraulic? Or self adjusting? Are they really worth the money on an outboard or IO setup?

Yes
Hydraulic or Electric.. I prefer the hydraulic. Bennett makes a really good one. Insta-trim are less money, and seem to be good quality also.
http://www.ebay.com/sch/i.html?_trks...at=0&_from=R40
They are worth the money

Made a huge difference on my ride. I went with lencos. Love em to death!!

I should clarify, I've got trim on the motor. Tabs still make a difference?

I have Lencos on my boat. Different hull but I don't want a boat without tabs.

i've been told trim tabs are like 4wd, if you ever have them, you will never go without them.
i have had my boat 20 years and still have not made the leap. i'm too scared to drill that many holes in my transom

Phatdaddy, check your pm's.

I agree with the "willies" and transom holes.

What do I really gain though? I mean over engine trim? Is it yaw, pitch or roll?

You're out with a few friends.. One of them is 350lbs and sits on the same side as you... the other is 145 soaking wet.. and sits on the port side. Your boat has a list to the Starboard side. You can push a button at speed and make the list go away.
You're in some heavy seas, and your bow is porpoising thru waves coming at you from your starboard fore-quarter. You push a button and force your bow a little deeper into the waves, add a little port-side trim and now your ride is smooth and stable as you cut through the waves instead of going up and over them..

They simply give you better control over your boat's port and starboard and fore and aft trim. Much more than your engine trim does.

No, they are not a necessity. Yes, they are well worth the cost.