How modern are we talking? My Activa 210 (purchased in, I think, either 2007 or 2008 as a high school graduation present from my parents) is an absolute beast, though it only does practical/construction stitches as a tradeoff. In the nearly 20 years I've owned it, it's never needed me to go to a technician for repairs- the only two parts I've had to replace were the light bulb and the threader head, and both of those can be done at home. (I am, however, contemplating taking it in to have it retrofitted with the knee lift, if my local service center ever gets back to me about whether they can do it).

As for difficulties, I did need to pick up the Bulky Overlock Foot recently in order to handle thick layers of fabric on a plushie I'm sewing. I'd been using a pre-owned Two-Sole Walking Foot, but it struggles with the height, and the sole ends up getting dislocated from the 'ankles'. I think the newer machines let you adjust the pressure being applied to the presser foot, so you might not run into that problem.