I've got a Dash that I bought fairly recently so that I could complete my Chumby set.
It works well and I have been able to register it to my Sony account and add channels, and then modify those channels. It's a bit slow to act on changes made on the website, but it will get there eventually.
One thing I particularly like about it is that you can set the display to show clock and weather on one half and widgets on the other. For this reason, it has a prime position in the kitchen.
Its timekeeping is a bit off - it's usually one to five minutes slower than all my other Chumbys and Infocasts. If it's power cycled and set to the correct time, then told to set the time off the internet, it will revert to the wrong time. It doesn't continue to drift further and further away from the correct time - it remains within five minutes of the correct time, so it's as if it's getting bad information from its time source.
In short, if you want a Dash and can get one for a good price (which you should, they're not getting very high prices on Ebay at the moment) then go for it. Eventually, one can only assume that they will stop working when Sony loses interest. But it hasn't happened yet.