Sure.
Problem 1: the actual upload(s) of the XAP to App Hub just failed sporadically - we got an opaque error code which, when we looked it up, translated to essentially "either there's a problem with your language settings... or there was a random network error." Eventually it just worked, with no rhyme or reason - one out of every few times, it would get through.
Problem 2: the first time we were able to complete the submission, the app was rejected because we had marked it for worldwide distribution. Turns out the [free] app was barred from three countries (China and I forget the other two) because it had a few "inappropriate" images (of museum exhibits). OK, fine, some countries are censorship-happy - not MS' fault. So what does MS do? Reject the app wholesale (rather than just in the problematic countries). We resubmit (going through all the difficulties of #1 above), exclude the problematic countries from the "where do you want your app available" checkboxes... and wait as it goes through the full 5-business-day approval cycle.
Problem 3: OK, the app is certified and made it into the store! Woot! But wait - it has a pretty serious bug - can't play any audio! (It's a museum tour, so that's rather unfortunate!) The bug didn't exist in the version we tested (in the emulator and two real devices), and after several days of back-and-forth with MS, they acknowledged it was a bug in the "XAP ingestion" process (what App Hub does to your XAP once it's submitted). They suggested a workaround, which we implemented right away (it was trivial, albeit not-really-obvious). At that point - this is after talking to several-layers-up support engineers - we asked that they push our update to the store ASAP (given that it was their bug we were working around). The best they could do is "expedite" the certification/approval process, which still took 3 or 4 business days - which doesn't sound like a lot, but is pretty absurd given that the update fixed a showstopping bug which was the result of MS's own submission process.
All in all, it took several weeks from completion to actually appearing in the store - which is better than the App Store at its worst, but not exactly awesome... and, FWIW, we only started getting real answers after several layers of escalation (which I suppose isn't terribly unusual, but again, not really confidence-inspiring).