I tried growing an Oxalis triangularis (very similar to O. regnellii but green instead of purple) a couple years ago, but it didn't go well; I gave up on it when it started to go dormant, 'cause I didn't know they'd come back. I know better now, but don't have that much interest in them. Maybe if they didn't have to go dormant every so often, but unfortunately they do.
I also have some concerns about why a dark purple Oxalis (family Oxalidaceae) with pointed leaflets and large pink flowers is considered an appropriate substitute for a green Trifolium (family Fabaceae) with rounded leaflets and heads of multiple tiny white flowers. One is a shamrock; the other is clearly something else. But I suppose strict historical authenticity is not the point, since it became a bigger drinking holiday than a religious / cultural one.
I concede that the Oxalis has much better decorative potential.