Here are the hubs that I've heard can be problematic, from Sturmey-Archer.

The 2-speed kickback hubs
The S3X fixed-gear 3-speed hub
The original (like 1950s-1960s) 4/5-speed hubs
The older narrow ratio 8-speed hubs

The wide ratio 8-speed hubs, especially current production, from what I've heard, are fine as long as you don't shift them under load (which none of Sturmey-Archer's hubs can really handle well). I haven't had a problem with my 2011-production X-RF8(W).

The current production 5-speeds, from what I've heard, are fine. The normal 3-speeds are bombproof.

The lowest ratio that Sturmey-Archer offers in their components for the 8-speed is 30/25, but they don't specify a minimum input ratio, IIRC. 30/25 is generally accepted as the lowest safe ratio, though, because of that.

The 8-speed was originally designed for small-wheel bikes (think folders and recumbents with 406 wheels), where cranksets could be relatively normally sized. Then, with the wide ratio model, they decided to market it for urban applications with 559 and 622 wheels, hence the 30T crank being a standard SA part in the S80 series.

Also, I've heard that even when the 2-speed SA hubs DON'T blow up, they shift poorly. I've got a vintage Sachs 2-speed hub (which is what SA copied) on my folding bike, and there's none of this "getting the hang of the shift" over 500 miles, it took me like 5 miles maybe to get a hang of it, and it just shifts reliably. If I had to have a new production 2-speed hub, I'd look at the SRAM Automatix, and mess with the spring to get the shift point right.