I have experience with two 11-87 Premiers, an 1100 Special Field, and an SPR453 when it comes to autoloaders. I can't compare them to the I-12 or m2000, as I have not shot them. To me, the 1187s are a much higher quality than the 453, but they all shoot reliably. The 453 shoots 3.5" and did need a long break-in period to shoot light loads which the Remingtons don't require. The 12 ga. 11-87 3" shoots 1 oz Remington Game loads through 3" turkey loads just fine. Had one jam out of a box of 25 old 1 oz loads..really old Alcan loads. It shoots straight, does not kick much, and is a nice looking gun to my eyes.
The 20 ga. 11-87 and 20 ga. 1100 I have experience with cycle 7/8 oz 1200 fps and the hot 3/4 oz 1400 fps loads just fine. I have not tried lighter.
They do get kept clean.. I don't take the autoloading feature for granted as some do. Two hundred rounds between cleaning..probably has not happened on any of them. We don't shoot organized clay games with them yet, and I don't do torture tests on my own equipment. They get cleaned every three hunts, probably, or every other time to the range. They are very easy to clean as was stated, except for the recoil spring which is in the buttstock. Cleaning that involves removing the recoil pad and then the stock to access it. It should be done once a year or more often if it gets dunked a lot. Probably the weak point of the design in my opinion. It is easy to overlook because it is out of sight..I think many casual owners don't realize it is there. If that spring and tube interior gets rusty you will have problems more than likely, at some point.
Fit is as important as function because Remingtons don't come with a shim system or anything like that. It is designed for what Remington figures is the average build.. I must be close enough, because these guns fit me great. I love the way 1100s and 11-87s fit and handle for me, particularly the lighter Premiers. The SPR453 fits pretty well but not quite the same... that grip is thicker, it is longer and heavier overall. In the looks department there is no contest. The triggers are better on the Remingtons, too.
The stock recoil pads on wood 1100/1187s are poor, though..it is basically a hard rubber spacer. The SPR453 has a plain rubber pad but at least it is somewhat soft. Some new Remingtons come with the new R3. It is a much softer pad - not much to look at, but effective. I'm not sure which 11-87s come with them on. With the R3, Remington is finally issuing a proper, useful recoil pad on their guns.
There are a bunch of different 11-87 models out there. The Sportsman is the "cheap" model - it has synthetic stock, more weight overall, and is more muzzle heavy than the Premiers, and sell for bit less. There are a bunch of other specialty models, too, that generally sell for more than the Premier.
Worc is correct that the 11-87 is not full of new features. No Gel Tek, ComfortTec, Mercury Recoil Reducer, Kick Off, Speed Load, Cryo Barrel, or Overboring. It is simple with only one button on it, and that is to close the chamber. Classic looks and classic function.
Jeremiah