I've completed my one week trial of Alloy Stems, and the results are positive. I didn't break or bend any of them, and after a full week of play that is quite a surprise to me following my earlier experiences with them.
My DartPro stats for the week showed an improvement of 2 percenatge points against the rolling 28 month average, and I scoreed two 180's with them - well above my usual average of less than one per month.
The problem with them loosening during play disappeared, so it seems a few good tightenings make the thread work better with the tapping within the dart.
I'm almost a convert to the Alloys, and I'll take them to tomorrow night's friendly game against the Wheatsheaf before moving on to trial the Harrows Titanium Stems later in the week.