> Does this now mean that I can never buy a lens cheaper online without trying it first?
No, I don't think that's true. For one thing, even Nikon doesn't always get it right. When the 18-200VR came out, I had to upgrade the firmware on two of my Nikon cameras to be fully compatible. One of them, the D100, is not field-upgradeable, and I had to send it back to Nikon to get this addressed.
To put this in perspective, I cannot remember a single instance of Tokina lenses being incompatible. Tamron may have had one situation with one lens about a year ago, but it was infrequent enough that I can't remember for sure. Sigma has had trouble with a couple of individual models, and more generally with the whole set of HSM lenses in the past five years. Usually when there is trouble it has to do with a specific feature, not the whole operation. For example, the D3 improperly reads the 120-300/f2.8 HSM lens as a DX lens, rather than as an FX as it really is. In order to use it properly, one has to manually switch the camera to FX, which is annoying but is also a two-second workaround. Sigma has been quite good about sorting out the problems at no charge to the user.
Sigma is more susceptible because they have been much more aggressive about new technologies in their lenses. They had internal motors at least six years before Tamron and Tokina, and they had OS (their equivalent of VR) at least five years before Tamron. Tokina has yet to offer a similar capability.
And to put another angle on this, I have owned six Sigma lenses, including 5 HSMs, along with nine Nikon bodies. I've never *had* to send any of the Sigmas in, since I never had a D200. Even most D200 users weren't affected as relatively few use the AF-ON button, which was the feature affected. My Nikon bodies range from the simplest (an F2) to some of the most complex (D3), so I have a fairly extensive range of experience. I should also note that I've never had ANY incompatibility at all with my three Tamrons and one Tokina.
_____ Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!