As a developer using OS/2 in its heydey and the early part of its decline I would say your assessment was spot on. Before NT the pre-emptive multi-tasking and ability to run Windows executables as well as OS/2 ones was a significant merit. Once NT came along it so clearly didn't have a future.
By the by "IBM VisualAge for C++ for OS/2" has to be a contender for world's least snappy product name.