I can't say they are overrated in my area, they don't sell for more than others of similar quality. I did mention it, but if I should emphasize their good points; easy to use functions, all levers, knobs, needle positoin, stitch pattern etc. are set with out any fuzz; my 730 has nice zigzag, at least as good as any machine I've used (often better), new or old. It feels solid and runs nicely. The freearm models have a narrower arm than most other machines, but it doesn't apply to the 540 of course. The 540 should be stronger and faster. A Bernina in a cabinet would go quickly in my area. They are generally easy to clean up and get going again.
I have to say, there aren't many other models that are just as good, but there are a few. The Pfaff 360/260 are much more work to clean and relubricate, they stick! You have to take out the cam mechanism and find optimal grease or decide to try oil. Berninas just need oil.
Much the same for the Japanese models with combo push-turn buttons, they need a lot of attention, and the various models are not of the even quality of brands like Bernina or Pfaff. With the finer points on stitch quality it's hard to tell if it's model specific or if it's down to adjustment or maintanance. I have heard of people insisting their model 15 has better stitch quality than their 201 and vice versa. Getting the right thread and needle match can make the difference, not so much a model issue.