This is an interesting lens, for a couple of reasons. First, it's a direct replacement for one of the film lenses that put Tamron on the map as a lensmaker: the company's 90mm ƒ/2.8 Macro 1:1 (still in production lo these many years later). First introduced in 1979 as the SP 90mm ƒ/2.5 Apadtall II with dedicated 1:1 converter, the film lens significantly undercut the camera manufacturers' expensive longer macro lenses in price while directly competing in quality—always a sound recipe for success with customers. By the time of the ƒ/2.8 AF revision in 1990 it also went to 1:1 (true "macro" magnification) without an extender, unlike some of its competitors at that time. The press release for the new lens notes that the older film version has been updated no less than seven times, which I did not know. Official sales in the thirty years since 1979: one bazillion.
The new lens features a bright maximum aperture of ƒ/2. Although exceeded in speed by Pentax's non-macro 55mm ƒ/1.4 portrait lens (which I've been shooting with lately), it's the fastest macro lens of its focal-length family today. In speed, it harkens back to Olympus's OM Zuiko 90mm ƒ/2 for 35mm, also a pretty special lens in its day. (Olympus also made a 100mm ƒ/2 "near-macro"—meaning it focused very close—that was one of my favorite lenses for years.)
Tamron's new lens also features IF, meaning internal focusing, meaning that the lens doesn't extend as you focus closer. Now, I'm not a macro photographer, and I'm quite sure to be corrected emphatically and frequently if I'm wrong, but as far as I know this is still pretty unusual for macro lenses, most of which extend in a manner that would make a Victorian lady faint.
No word on dates or prices yet that I know of. Mounts: Canon, Nikon, and Sony (in all cases for APS-C cameras only). The optical construction is an elaborate 14 elements in 10 groups, minimum working distance is 100mm (~4 in.) from the front element, and it has full-time manual focusing. Size is 80mm (3.15 in.) in length by 73mm (2.9 in.) in diameter, and it weighs 400g (14.1 oz.).
(Thanks to Robin Pywell and Adam Maas)
Featured Comment by T: "Of course, I hope it's good, but I'm not entirely convinced of its utility.
"In the non-macro, wide-aperture department, it also has to compete with the 50mm ƒ/1.4 and ƒ/1.8's (or, on Pentax, the 55mm ƒ/1.4; or possibly with the manual-focus Voigtländer 58mm ƒ/1.4).
"In the macro department, longer is often better—for the sake of working distance (as long as it doesn't get out of hand for indoor work; things are still fine at 90mm). A 100mm working distance at 1:1 would be something, since the Tamron 90mm macro has a 95mm working distance from the filter ring (not the front element). But the latter hardly needs a hood, since the front element is deeply recessed. With a hood, the working distance of the new 60mm might get cut down quite a bit.
"I would have rather Tamron came out with a competitor to Sigma's 150mm macro (which occupies the sweet spot of being significantly longer than the 90/105mm macros, but much cheaper than the 180/200mm macros)."