Rough auto shifting question:'93 90S

[Ed Skladany <eds@njcc.com>]

You folks gave me tons of great info and discussion on
the merits of buying one of the various 90 models.  Thanks a lot!

But...one of my main questions didn't get a direct answer
so I'd like to ask it again with a different 'subject' title
to attract a different audience; it's all in the marketing.  (-:
Sorry for the duplicate question, I just need to know.

Here's the original question, slightly edited for context:

I'm checking out a '93 90S to buy.  It's got 138K miles, but feels 
good to drive.  One thing concerns me; I think I feel a slight roughness
in the auto-trans during up and downshifts, and maybe a slight delay
after power is applied, but I'm more sure of the roughness than 
the delay.  I'm an ex-mechanic so I'm attuned to this stuff.

My '84 4000S is a stick so I'm comparing the shifting to my wife's 
'85 BMW 735i, which shifts pretty smoothly.  My question is: does
this sound normal for a '93+ 90S 4-speed auto, or are the clutch packs or
something else starting to go?  What's a reasonable life-span for
this trans?  
 

Thanks,
Ed Skladany
Hopewell, NJ
eds@njcc.com