Thanks for your replies
I tried out the testshard, it was stable but not playable in the "I want to advance my character" sense. There were interestingly designed but empty buildings, and no items or npcs save for a couple of goblins.
I've tried Iris2 on my prefered regular client shard, Excelsior. Unfortunately the shard has a lot of custom content that does not appear in Iris2, and it crashes pretty quickly when I'm around where it is supposed to appear.
Another issue that you're likely aware of is that custom gumps or UI popups tend to be unusable. For example, in defianceuo there are skillballs, and the UI for them comes up in the right size, but there is no text for the skill names. Similarly, I'm afraid that the captcha (to report unattended macroing) UI in Excelsior probably won't be completable.
Thanks for your friendly support and hard work.