I can't speak for internal testing but from personal experience I can only say I've tried my best. Starting with a memo in January regarding the most important EU issues with regards to eCommerce.
And I've continued to cause head aches around the globe by doing an extensive test matrix of nearly 300 different check out scenario's. I've extensively tested 4 builds between 4.4 and 5.0 all focusing on practical check out scenario's and usage....
No, there aren't any blocking issues with configuration. The basic configuration hasn't changed since v4.4 - if you need a hand with it, feel free to contact me or watch the "From start to multi-lingual checkout with Sitefinity 4 in 15minutes
Yes, page ordering/hierarchical sorting has gotten worse with v5 - was it tested? Yes. Was it flagged Yes. Did it get fixed? No unfortunately not. Where as in v4 sorting was an issue with taxonomy, with v5 pages seem to be affected as well...
Not sure what you mean by configuring a shop module, those things work although in future versions they can be made a tad more multi-lingual friendly. But the move from v4.4 introduced variations into v5 fully multi-lingual was almost flawless.
Sitefinity 'mobile' is just in its version 1 release, basically meaning 'this is the basic functionality which will be matured in the next version'. Currently there isn't an option for different widget templates for normal vs mobile. So naturally things will go quirky. Internally they're probably already working on a way to address that but for now, the column switching is an 'idiots' way of doing responsive design. If you don't like it, copy and paste it out into your own css.
Yes the iPhone preview has a bug with IE9 but Chrome, Firefox, Opera and Safari all work and besides it's a 'preview' if we're going to be picky lets focus on the fact that 'orientation landscape' is forgotten.
And lastly, with regards to translations, you basically get what you put into it... With v4.4 I delivered a whole bunch of proposed changes in the desired excel format. 20 minutes later I received the completely updated v4.4 Dutch language pack and Telerik updated it on the Marketplace.
Forgive me if I've taken it a bit personal when you say "NOT TESTED" after +500 manually performed check outs for this release, but in this case I think the only fair point to make is that hierarchical sorting got worse...