[LausDeo]

I have one. I've only been able to fire a few rounds with it but I do have some points to offer-

The post is definitely thicker than a normal post. But at least on the XS tritium sights (the ones I have), you also have a thinner white bar surrounding the tritium. I think if you learn to use the width of the bar instead of the whole post, you could be very accurate. That's what I'm hoping for.

In the dark, the rear peep is damn near impossible to find. I can see the front sight but not the rear, which means it would be best reserved to close quarters scenarios (not like you're going to shoot something off at 200 yd at night anyways). HOWEVER, every time I've looked at the sights in the dark, I did not allow myself the time to let my eyes adjust to the darkness. If you've been out in the dark a while, it may be possible to find the rear sight and get much better accuracy out of the weapon. Also if there is any low-level light from a nearby town, house, or whatever, it's probably enough to find the rear sight. You may not get the greatest picture, elevation being the primary issue, but men and most dangerous animals are taller than they are wide anyways.

That's my $.02, YMMV

 

[mercman]

I just picked up a SEI dot FS. I have yet to mount it on a rifle but should get around to in the next few weeks. I'll post my impressions then.

 

[mars]

I have a sei bar type and I think it works really well maybe not as a standerd usgi but much better than the xs that came with my socom the xs is just to fat to use for distance at daytime in my opion but I haven't used the sight for night yet

 

[mariodesmo]

I have one on my Socom 16 and I would second everything LausDeo wrote
above. I have used mine in darkness but you (I) can't really see the
rear sight, so it makes if difficult to know where you're aiming. If at all.

I think you really need a rear tritium sight to align your sights.
Without having rear sights illuminated to properly align the front, you never
really know where you're aiming in the darkness.