Windows programs - up to and including Windows 3.1 and some win32s, provided they're not using a vxd. No it cannot run anything DirectX related.
Security - define 'secure'. It's a resolutely single user operating system that can also run server services. Technically the screen saver can be locked, people never really did.
Ease of use : some parts are superb, others - less so.
Driver support : ok, provided you fit your hardware to OS/2 rather than try and do it the other way around.

eComstation is a tad newer and should 'just work' on modern systems without patching. Warp 4 should also run on modern systems with some coaching.

It's probably easier to stick it in a VM. There's only a few games worth playing on it, and whilst the interface and multitasking were lovely at the time, it's really most useful if you already have a background in OS/2 and software for it.

I "won" OS/2 Warp Connect 3.0 (with the Red Spine) at the grand opening of a local computer store in 1994 (or early 1995 - can't quite remember).
It works great with Windows 3.1 applications, but not so much from a gaming perspective. Back then, most games were still developed on DOS.
When Windows 95 came out a year later, it basically spelled the end for OS/2.

I think one of the problems with OS/2 3.0 and 4.0 (purely from a general user experience) is its poor compatibility with MS-DOS based games and applications. It was actually much closer (in terms of its kernel) to Windows NT.
This is where Windows 95 had the advantage, since it still offered MS-DOS compatibility (either within a DOS window or MS-DOS mode) for older applications that ran on MS-DOS. And, of course, DirectX.

I think had the market moved away from MS-DOS earlier, then the picture could have looked a bit different today and there might have been a larger adoption rate of OS/2.
However, despite Microsoft's own attempts to move away from DOS in the early 90's, the market hang onto it a while longer, until Windows 95/98 became more popular and the market moved away from MS-DOS as the main OS.

It does look promising from this 1994 video. They claimed it worked great with Microsoft software... Maybe the earlier versions OS/2's were better?

https://www.youtube.com/watch?v=mmxabyk0S2M

No, the earlier versions of OS/2 were worse. OS/2 2.x onwards have very similar DOS (actually, any real mode operating system can be run) compatibility, with lots of things to tweak. Its compatibility is generally better than 9x, but 9x has the advantage that it's possible to drop back to real DOS and run a game - OS/2 can't do that, you're always running DOS programs in v86 mode.

Windows 3.1 compatibility is excellent, and it offered the ability to run different programs in separate Windows sessions, meaning a crash of one Windows app wouldn't take others down (used more memory, obviously)

Connect red spine - in fact any 3.0 version can be brought up to the same kernel level as Warp 4, although the networking components will be a little further behind (not really an issue).

Games wise I still love Galactic Civilisations 2, and Avarice was interesting but ultimately not a great game. There's some other decent games but they're available cross platform.

My main retro system still runs OS/2, but for day to day use I'm going to make an OS/2 VM and stick some of my applications in that. OS/2 doesn't support 3D acceleration, and most hardware you'd want to run on it can be emulated, so there's not too much point using real hardware for anything other than nostalgia's sake.

OS/2 1.x had awful DOS compatibility, as it's a 16 bit protected mode OS. I'm planning to get it working on my 486 retro PC, but it's very picky about hardware, and the selection of high colour graphics card adapters is extremely small.

Ultimate OS/2 Warp 4 machine?

😀