This cap is still going strong and continues to be a favorite. I've not yet experienced any leaks, and the D-ring is as sturdy as ever. I sometimes clip the bottle onto bags, bikes, etc. for easy access. Haven't had a problem doing this. I've also put it through the dishwasher a few times with no ill effects, though I don't do it often. I'd still recommend washing by hand on most days.
Since moving from the classic Klean Kanteen style to the wide mouth version, I've lamented the loss of the stainless flat cap. Those of you who have a classic bottle with this cap know what I'm talking about. The flat cap was flat (as you'd expect), and needless to say, very compact.
The Klean Kanteen wide bottles come standard with the loop cap, which has a relatively high profile. This D-ring cap falls somewhere in between. It's not quite as low-profile as the classic flat, but fits better in bags than the loop cap. The ring itself is quite sturdy and easy to clip onto things, and falls flat when not in use. It fits fine with both the insulated and noninsulated wide bottles. I've never tried it in a dishwasher, but I would recommend hand washing anyway. I believe it does have a gasket in there, so to extend the life of your cap, hand washing is probably best.
If you are wondering about its plastic content, well yes, it's made of BPA-free plastic. The inside of the cap where your water would come in contact with the lid is stainless. There's not much else to say about it, except to add that I've never had a leak with it so far.