I know owners brag something awful on their new Bernina and Husqvarna models, it's not the reasonably priced once, fancy models with fancy prices too ;- )
If you ever should have room for a vintage machine I can tell you they are very nice and dependable, and I say that comparing to any machine out there. There are lots of nice machines though, used and brand new. You really need to try the machine if you buy it mostly for the buttonholes, some models make them trouble free with sew-all weight thread on two layers of shirt fabric, but struggle with coat fabrics, top stitch thread, loosely woven fabrics,... In theory:, if your Elna is a low shank, can drop the feed dogs, it should work well with a buttonholer attachment. It depends a bit upon the needle clamp though.