I am very interested in the answers and tips on this subject. I purchased dedicated needdles from Schmetz for the purpose but never had the gut to start. My Janome machine discourages the use of leather so check your machine instruction book.
Hugs, Roberta

I have not, but picked up a few hints from Anita Goodesign and a few different classes. You want a thinnish, supple leather. You want a fairly loose design, so the edges don't drill a cut line or tear line in the leather. For example, if you did an applique, you would want a blanket stitch edging or zig zag rather than a more solid edge. I have read to use the leather needle and have read that it is not necessary - take your pick.

I have. Not only small items like tissue covers, but I also stitched over an irremovable spot on my sister's very expensive light blue suede jacket.
Use a thinnish leather like nappa or suede, think shoe-uppers or handbags. A leather neadle cuts triangular holes, necessary for thick leather, not for the thinner ones; it only increases the risk of tearing. Just use an all-purpose or embroidery one and with a not-too-dense design you're laughing.

Great advice below...it is very similar to stitching on vinyl... Here is a You Tube Video for Embroidering on Leather that might be helpful

https://youtu.be/lZZtjoShYz8

I stitch on customer leather alot.......I find I do not have to use stabilizer and I use a standard needle......I slow machine down a tad and I also thin out my underlayment......I added some pics for you to see......