The password issue did indeed affect only a small minority of users. However, there are dozens of other issues which affect most users. This update has been the biggest screw-up for some time, and whoever was in charge of the development has really messed up.
The first problem we encountered was Saturday night when I started getting SMSs from our server about failed payments. Contacted SP, who insisted that there were no problems at their end. After about half an hour of debugging, I found the problem - their SSL cert on the new server was broken.
After resolving this, we had several 10-20 minute down periods on Monday.
But this was just the beginning. The biggest issue is that the new user interface is a complete mess. It's the worst example of what you can do with grid controls, iframes and ajax. Usability is terrible, and it regularly throws up 'Oops, this operation did not complete' errors.
On top of that, you are limited to an 800px wide iframe, which means you have to horizontally and vertically scroll to do anything.
Common tasks take about twice as long with the new interface as they did with the old.
The old interface worked - it was dated, and could have done with a tidy, but it worked. What they have built to replace it is a fantastic demonstration of how not to build a UI.