Why are some people so particular about buying an "is" car?

[blunttech]

I always look for the cleanest I, IS whatever I can find. All that crap is going to get changed out and upgraded anyway.

[Quadrajet]

There is some suspension refinements with the "is" as well. And sometimes an Mtech steering wheel.

[ME30W]

I've seen numerous WTB ads recently that are looking for a 325is, not a 325i. As far as I know, they are essentially the same car while an IS has a few body add ons, sport seats and an LSD (which was an option in the I anyways)

Are there truly any advantages to an IS car? Or are IS owners out there just riding the wave and charging a bit of a premium?