I haven't tasted one, but I planted one this year that I got from Cummins and I'll have a bit of scion wood if you'd like some.
Here's the description I cobbled together from various web sites for my notes:
(Bloom: Mid-Late; Ripen: Late September/Early October)
A cross of ‘Dolgo’ and ‘Haralson’, Kerr is one of the very best apple-crabs. Stores well, good fresh after a mellowing period, very productive. Originated with the Morden Research Station, Agriculture Canada, Manitoba, selected and tested as ‘Morden 352’, and introduced in 1952. The tree is moderately vigorous, broadly upright, round-headed, has strong wide-angled branches and is annually productive. It is hardy to Zone 2a, and moderately resistant to fire blight. The fruit is medium-size, 1.75” in diameter, oblong oblate, long stemmed, with shallow stem cavity and basin, and matures in late September to early October. The skin is creamy yellow, completely covered with crimson and later maroon, and covered with a medium bluish bloom. The flesh is yellow and tinged with red, very firm, very crisp, very juicy, somewhat tart but very sweet. It is very good for fresh eating (better with storage), excellent for cooking and canning, and superb for juicing. It has excellent storage capability for up to 27 weeks. The taste is really intense if picked on the young side, though it mellows somewhat it if given a couple extra days. It tastes somewhat like a ‘Haralson’, but it is extremely juicy.