I used a pair similar to the ones you can get on ebay or Amazon for around $12. They make a chrome version as well.
Pros:
-Cleaned up look and profile. The REs I've seen using the bar ends simply look like they are lower. Even give the illusion of a time before bike had mirrors because they kind of disappear in the profile. I like the way mine aren't very noticeable, which is why I chose black.
-They don't vibrate. The stock lolly pops I had before were pretty much useless because of the vibrations.
-The ones I have are so cheap, if you break them, you can easily replace them and still be under $25
Cons
-Have to alter my view slightly to see them. Not usually a problem for me, my riding style is to look several times by turning my head rather than rely on mirrors anyway. They mostly get used when I'm at a stop watching the bozos behind me for signs that they're going to stop.
-Have to cut/modify the ends of the hand grips. The Iron Barrels didn't come with bar end weights that can just be screwed into or have mirrors attached to. You end up having to cut part of your hand grips off. The passenger side is easy, but the right side has to be done in a way that the throttle still has free movement. The result is a slightly shorter hand grip, and less surface area to rest your hand, but you get used to it and don't even notice after a while.
-These particular ones don't 'break away' so if they get bumped hard and are synched down tight, they may break. The flip side would be bar end mirrors that do break away, which sometimes means a joint in there that make them slightly more bulky.