I feel for everyone having problems with their 7xxs, but for those railing against SD - most of whom don't even own a 7xx, btw - I think it's important to remember two points:
[1] first gen + complexity
This is a first generation device. Every highly complex first generation device has bugs to work out, whether it's recording gear, cars, etc. Even Grace Design - who generally receives nothing but rave reviews for customer service - had trouble with their first gen V3s: miscalibrated low-batt indicators, DC offset, etc. Granted, the problems only affected a relatively small number of units, and far as I know none rendered recordings unusable - but nonetheless, there were problems.
Now consider that the SD 7xx boxes are substantially more complex due to the HD and surrounding features and PC-connectivity, and it's no surprise there are issues. While the problems are frustrating, certainly, what's important in my mind is how SD responds to the issues customers are facing. So far, it seems they've responded reasonably swiftly and favorably in addressing known issues.
[2] the nature of online forums
There are likely plenty of people using 7xx boxes with no or minimal issues. Forums like this tend to bring out primarily negative comments as a sounding board for people trying to resolve problems. The satisfied users simply don't have a reason to post - they're too busy enjoying their new gear!