The first version of OS/2 Warp to provide peer-to-peer networking to OS/2 and Windows machines. These networking functions were later added into the regular product line. See OS/2 Warp.

That alone is a significant difference between Microsoft's OS/2 2.0 and IBM's version: Big Blue didn't include networking until Warp Connect 3 in 1995. His verdict? Over at Virtually Fun ...