About a year and half ago I got a Das Keyboard Ultimate for work, but immediately had some major issues using it. Fortunately, the 10-year-old keyboard it was replacing wasn't completely unusable, so I just switched back. That keyboard finally gave up the ghost a couple weeks ago, unfortunately, so I was stuck with the Das Keyboard. And even though they say it'll work across a PS/2 adapter (though not the built-in USB hub, of course), I couldn't get my machine to recognize it through PS/2. Not sure what the issue is there.
After a couple weeks, I've actually adapted most of the common "scan-inverse pairs" and type them more slowly to avoid errors. Unfortunately, there are a lot of such pairs, and some of them occur fairly infrequently (e.g., "oa"). So I still have a lot of screwups with the infrequent ones, but the common ones (e.g., "th") have been addressed with muscle memory. Kind of pisses me off my "ultimate" keyboard has trained my muscles to type sssllllooooowwwwweeerrrr instead of faster. But whatever. Probably the most damning inversion, however, is due to BACKSPACE being late in the scan order. So if you have a one-character typo and hit BACKSPACE followed by the correct character (especially a left hand character) in rapid succession, it almost invariably types the new character first and immediately deletes it, leaving the typo untouched. Arrrgh.
I've also noticed a suprising amount of wear on the keys for a couple weeks usage. The spacebar has already completely lost it's texture along the bottom edge and the letters (especially the home row) are noticeably polished. Same for BACKSPACE (which I end up using a lot now), ENTER, and the left-side SHIFT, CTRL, and ALT keys.
On the positive, the action is really nice. I'm a fan. I think the weighting of the keys is a little light, but I type hard. The keyboard as a whole is also really heavy so it doesn't slide around on my desk, particularly when my right hand is dancing around between letters, the numeric keypad, and the arrow keys.
Their site says that they've redone the electronics to not have such issues with concurrency, so hopefully that's true. It looks like they may have also reved their switches, which probably will change the action to some degree, as well as making a less clicky version available. I'm certainly not going to spend $130 for a next gen version without getting to test drive the new hardware first, but in the meantime I'll probably keep using this one.
So guessing you are not recommending this keyboard eh. Don't know why you did not send it back in the first place for a refund – sounds like it's not fit-for-purpose, which is a sure fire way of getting a refund in the UK. I don't think I would pay $130 for any keyboard, unless it typed for me, but one that can't keep up with my typing. I have a Cherry that cost £20 which is now 10 years old and still kicks the arse of any other piece of crap I have the misfortune to lay my fingers on!
If you're looking for a good mechanical keyboard check out the Filco Majestouch. Uses the same Cherry MX (various colors based on "feel" and "noise") keys. For other alternatives check out geekhack.org.