My understanding is that even though nobody will admit to their actual capabilities, it's fairly widely believed that stealth doesn't work anymore.

While the radar cross-section might be the size of a large bird, which is always a major bullet point in their marketing material, no large bird is flying in a straight line at 5k+ feet and 400 kts and it's easily within the the capabilities of modern processing to sort out all the large bird sized objects and find the one that's behaving in a very un-birdlike way.

Of course, I suppose it's always better in a war to be seen as little as possible, but newer projects like the F-22 and more specifically the F-35 are probably handicapped by being held to meeting the "stealthy" design requirement.

There are limits, of course. They are only stealthy under certain circumstances, it requires the radar installation to use certain wavelengths, and they need to avoid flying in front of another target (or there will be a stealth plane shaped hole in the radar return).

I would expect it to still work just fine against a single older export style Buk installation, but perhaps not so well against the newest ones used by the Russian army (and although I have heard nothing about the Chinese equivalents, I expect the same would apply).