delay in shift

I've noticed since I purchased my Sable 2 days ago (2001 with Duratech and 36K miles) that it shifts wierd from 1 to 2. Its like there is a pause in between gears. All other gears shift smooth and promptly, just the 1-2 shift. If I hammer on it good off the line it does it and also if i drive very slowly for the shift. It only does it when the car is at normal operating temperature as near as I can tell. I'm gonna hopefully put a tranny cooler on it, do fluid and filter and add some transmission additive (slick 50 maybe?) Any suggestions? My speedo and tach work, no dummy lights which would rule out the VSS. I can also slightly feel the car bump back into 1st when slowing down, around 5mph.
Help me out, or I turn around and sell this thing before it up and dies on me....

c'mon, anybody care to way in?

well I went to the local ford dealer today, and took a few used tauruses for test drives for comparison. I drove an 04, which shifted like crap despite being certified pre-owned and only having 31000 miles on it. I then drove an '02 SEL Taurus, with 50,000 miles on it, and it was pretty smooth, but not much better than my sable. Anybody know if its normal for the car to have a bang noise when shifting into reverse? I had a 97 Lumina for 3 years and it did it the whole time till I sold it. No problems. Is this true for Taurus too?