OS/2 Warp's killer feature was an excellent TCP/IP stack, enabling people to use the Internet without voluminous and hacked-together third-party software.
There was nothing wrong with Trumpet Winsock for modem users. For 10b2 users, the official microsoft stack was adequate. TGV Multinet was a high-performance stack for Windows 3.x which was more than adequate. Sure, you had to have third party software, but there was nothing particularly hackish about it. At the time, you had to deal with equally hacky software to get SLIP (let alone PPP) connectivity on most platforms. Only Unix-based and Unixlikes seem to have come with TCP back then.
Warp cost more than Windows plus a TCP stack...
The killer feature of OS/2 was multitasking that worked. Problem was, nearly nobody had enough RAM to really take advantage of it.