and later are narrower in the nose, slightly less wide in the rear, have a more pronounced taper toward the front, have a thicker lumbar bolster pushing you closer to the bars and a different seat pan that sits lower in the frame. On 08 and 09's, the "soft touch" seat is now standard, it is simply an 05 and up seat with an extra layer of very soft poly foam. The height adjuster bar 05 and up has less "reach", so you can't get as high off the ground EVEN on the high setting. Staples are used to attach the vinyl on 05 and up versus rivets. The rubber bumpers on the bottom are mounted differently. "greige" (gray) was offered starting 05. The vinyl was changed in 05 to a softer look with no fake grain ridges. The 05 and up vinyl is not as slippery. The black color on the 05 is more of a charcoal black than true ink black of previous years. The pan on 05 and up is made from fiber tech instead of molded plastic. The polyurethane foam on the 05's and up is slightly
more dense. The comfort seat offered starting 05 and up has stitches and two pressure causing seams exactly
where you don't want them - nice!
I think that about covers it.
But I may have missed something.
Generally speaking, larger guys favor the 99-04 seats where smaller guys like the 05 and later seats.
There is no doubt in my mind that BMW changed the seat JUST since they were getting so many complaints from smaller guys that they couldn't reach the ground when in the showroom. It was hurting sales...
They are all interchangeable with a little modifying/trimming that can be easily done in your home garage.
ALL of them pretty much suck from a comfort standpoint, but then again I have a rather biased opinion!