Malcolm: from what I've seen, it's a two-way thing -- Miele is picky about dealers, they want people to have all the support they can get, and sometimes, when clients complain about the dealers to Miele, they can lose the account and then they badmouth Miele.
Having used Miele products, I can see that they are not for everyone. They tend to be very well built and with thoughtful features, but they were built for European people who have different needs and standards. If your needs and standards happen to align with them, you'll love the products... on the other hand, if your needs and standards don't align with the appliances, you may hate them -- I've seen people complain about way too many things (like for example, some weird dishes either don't fit on the racks or take a lot of space -- that happens to other machines too, not all dishwashers fit every single dish perfectly, duh) that wouldn't go noticed on any appliance that was on the two-hundred bucks builder special range, but once you bought the TOL couple-thousand bucks, people expect the moon, a pony and a grand piano too. Needless to say, it's hard to get that.
Also, with Miele in particular, I find that people say "oh, it's all the same and same quality, don't buy the 2,500 bucks TOL, get the BOL and you'll be fine" -- you won't. It's not just the build quality, dear, it's the whole package. While I don't advocate that people should get the TOL just for the heck of it, I do think that they should actually look at the products and think. Will you be miffed if the cycles always take 2 hours? Then you may want a cycle for lightly soiled dishes and another quick (30 min) cycle to refresh stuff during parties. People are used to "all I need is a rinse-and-hold, a regular and a pots-n-pans cycle", but with Euro-style dishwashers you do tend to use the different cycles more -- American-made machines tend to have very similar cycles because they want to top the charts for Consumer Reports, which tend to test dishes that were soiled and dried overnight with the Regular cycle; Euro-style machines have a light soiled cycle for dishes that were just taken from the table and run right now, a regular cycle to run at the end of the day when you were collecting the dishes for the day, then a Heavy cycle and a Pots-n-Pans cycle, which are progressively more intensive. If you are one of those people who'll scream "everything used to come clean in the regular cycle with my old such-and-such machine" without noticing that your old machine took 12 gallons per cycle and did a wash-rinse-rinse-wash-rinse-rinse cycle (which is essentially Pots-n-Pans now), you'll be disappointed. Miele and Bosch, more so than most other manufacturers, have several different racks, as the machines approach TOL, dishes that wouldn't fit or take too much space on the BOL racks will fit just fine in the more expensive machines. You can fit an awful lot more stuff in the TOL than in the BOL Mieles and Boschs. But make no mistake, more money doesn't mean you'll love it more -- I know way too many people who absolutely hate the silverware tray on the newest machines -- make sure that your silverware either fits those spacers or that you're OK with replacing your silverware, there's very little room for compromise there. Also, some of the MOL Mieles have a silverware tray that doesn't split and the TOL ones split. There are people who love one and hate the other and you'll have to decide for yourself. If you don't think you'll fill the tray every time, the one that splits will let your remove the smaller part and then you can add very large bowls and tall stem glasses on that side of the rack, but people who use a lot of silverware tend to like the one that doesn't split. Also be aware of the fact that most largish things like spatulas, ladles etc will need to go in the other racks, so you'll end up using the folding racks for that, probably, because it's unlikely they'll fit in the silverware tray.
So, as you see, it's no accident that in some places Miele has bothered to build showrooms where there'll be trained people who can answer your questions and suggest alternative ways of doing things that will work better for you. Most stores would have a problem with people who bought and then returned a 2500-buck dishwasher, for example, and they want you to get it right the first time if possible. Most people would spend a couple of months getting used to a new way of loading their new dishwasher if they are in the 300-600 dollar range, but they get huffy if they have to relearn how to load a new high-end dw. But the ones that are patient enough more often than not love their new machines (Miele or not) and claim they feel like they should have done that sooner.
Just take your time looking at the several different brands/models etc and think about the pros and cons. And I can't stress this enough: bring several of your dishes, both common and weird-shaped ones and try the different machines on the showroom. People who were all set to get one brand or another or a specific model often end up getting something else so their dishes will fit and they are usually the ones that don't regret their purchase, people I've seen going around with the "they're all the same, what's on sale this week?" attitude are usually the ones that regret their purchases. Not, mind you, that I think we in this crowd want to spend as little time as possible in the stores choosing appliances... ;-)