Millerhunter,
I have Bushnell Holosights on my Benelli Nova 12ga slug gun and my son's 870 20ga, and a Bushnell multi-reticle red/green dot on my 870 12ga slug gun. I haven't done any checking at 150yds, but I sight in at 100 yds and I think they are great. While I do love the holosights, they are pricey (I got great deals on both on e-bay though a couple years ago.) For the price, I really like the Bushnell multi-reticle (Model 730135, about $70 street price, and typically available on eBay for about $50). It has four different reticles as well as red/green selection. The green is really nice for lower light time in the woods, while the red is better for the bright sun. One of the dots is either 4 or 6 moa, I don't remember exactly. The nice thing is, with a rifled barrel and sabot slugs, the slug will pretty much be in that circle out to 100yds, and probably pretty close at 150yds. So, if you can see well enough to put the circle on the kill zone at 150yds, it should work fine. At the 50 to 100yd range though, it is fantastic.
Here's links to the ones I use:
http://www.bushnell.com/general/rifl...ht_51-0023.cfm
http://www.bushnell.com/general/rifl...hy_73-0135.cfm