In response to a few comments about buttonholes here are my thoughts:
First of all many times buttonholes are demonstrated during the sales pitch in the best of all possible conditions. This means a cotton fabric like twill that gives lots of places for the lock stitch to bury and so looks nice and neat, and a sharp needle - a 70 denim is the sharpest of all needles and gives the best stitch. Stablizing helps a lot too.
That's why the buttonhole in the dealer's may look better than you feel you can do at home. There are a few things you can do yourself however that will make your own buttonholes look better:
1. Use a new sharp needle. A friend of mine who was a great shirt maker always put in a new needle just before he made buttonholes - he had noticed that often he got a skipped stitch or two in his buttonholes (using the same needle he had made a whole shirt with) and this eliminated it. He then left the new needle in to start the next project.
2. If you don't already, and if your machine doesn't have some sort of default for this (or like the Bernina have a hole in the bobbin case to thread through the bobbin thread just for buttonholes, effectively tightening the lower tension) loosen your upper tension to about a 3 or less so the lock stitch join is pulled towards the back - giving you the smoothest possible satin stitch on the right side.
3. If you fabric is light and tends to tunnel or pull with a tight satin stitch, stablize your fabric behind the buttonhole area.
4. Use a cotton machine embroidery thread to make your buttonhole. This is fuzzier than sewing thread and therefore fills in the spaces between the stitches and makes a smoother satin stitch for your buttonholes.
Some buttonhole realities.
Don't make yourself nuts trying to figure out why the right side of the buttonhole looks nice and the left side looks messy.
This is just going to happen in any buttonhole that sews down one side and reverse up the other. All machines sew more effectively in forward than reverse. A buttonhole that is designed in an automatic system to sew both sides forward (usually this is achieved by a reverse row of straight stitches up the second side that are covered in the second row of satin stitching) will generally always look neater in my experience.
Always make your test buttonhole in interfaced fabric with the same layers as the garment. This will eliminate the surprise of buttonholes that suddenly seem too small for the button.
For the most stress free buttonhole experience you can always invest in an old Singer buttonhole attachment (eBay is full of them) and a simple straight stitch machine from a yard sale even (must be one that is low shank and has feed dogs that can be covered under the attachment). This attachment uses metal cams or templates that sew identical buttoholes, noisily, on light to medium weight fabrics. Completely foolproof with either keyhole, or my favourite, round ended buttonholes.
I have this set up on a small Janome at my shirt button default and can do a row of perfect button holes in about 5 minutes.
For fancy automatic machines with buttonholes that are a disappointment you can still make up your own system by playing with your zig zag, the right width and density for sides and the end, and of course you can swing this around to make a buttonhole that sews forward both sides.
I finally did this with my 7570 and wrote down on a little paper the settings I liked. A bit fussy but better than unpicking a messy buttonhole. For the Pfaff 7570 or 7550 you can usually get a fairly decent buttonhole if you use the default on the first display screen and always, always use the buttonhole sensor unit.
The problem with the Pfaff buttonhole, in my opinion, is that the sides are sewn in the opposite direction and that the sides are sewn too close together- it can be nearly impossible to cut the buttonhole open without cutting some threads. Too bad in machines that have that wonderful built-in walking foot.
Now what did I forget?