Autodesk showed AutoCAD v2.5 in June 1986 at the AEC Systems show in Chicago. I have Autodesk's brochure from back then, and it's interesting to read what was considered "new" in 22 years ago:
-- AutoCAD had more than 50,000 users.
-- Autodesk recommended 640KB RAM, but this release of AutoCAD also had Expanded/Extended Memory Support for computers running the then very expensive 80286 CPU.
-- regen-free zooms and pans.
You can see the list of new commands in the figure below. Autodesk cheated by making the ellipses from short polyline segments. Real ellipses would come later. Still, you can see why v2.5 was such a hit, because these basic commands had been missing 'til then.
(There is one typo: Table Menu is asterisked as a drawing command; it actually refers to the addition of a tablet overlay included in the box, which killed a number of small third-party developers who had been creating custom templates.)
As well, there were enhancements, such as these:
-- context-sensitive help.
-- Crossing and Previous selection modes
-- Polar option for the Array command
-- Mirror could now make mirrored copies at any angle
But not all new features have remained to this day. IGES im/export was later removed. As was the much disliked hardware lock (withdrawn a few months later with v2.52). Autodesk spun the unwanted addition this way:
AutoCAD 2.5 is execution-protected with a hardware lock. There are no power wires to trip over or take up outlet space; the hardware lock simply connects between your pointing device and computer.
At the time, Autodesk had hired a new marketing guy from IBM. As I recall the story, CADalyst (the only magazine dedicated to AutoCAD software at the time) could get a review copy of AutoCAD v2.5 with a 90-day invoice. After 90 days, we could return the software, or pay $2,500 (I think that was the price). Fortunately, saner heads prevailed: the new marketing guy was let go, and the 90-day invoice torn up.