I purchased a Lumia 920 last week for my wife and me (we're absolutely loving it!), but we have noticed an issue that I don't see on forums here.
Essentially, when we send text messages, especially longer ones, many times the we get a returned "can't send" message. It requires one or two tries more before it gets sent. The "solution" is to wait for a minute or two on the text messaging screen before it is sent. Even if you start writing another text to that same person it can disrupt the sending process. I have started a forum at WPCentral and have found out that it is not just my network (Rogers in Canada) of just the 920 (reportedly it has happened on the 8x as well. Here is the forum discussion: http://forums.wpcentral.com/nokia-lumia-920/203862-text-message-issue-920-a.html
On a side note (maybe related?) I noticed that when I am texting, many times it says one text is only 70 characters, and then with the second text it is 134 characters. This seems wrong to me (and to my provider Rogers). Is it possible that WP8 is misreporting how many texts are going through and this is causing the problem? Just a thought.
Thank you for any help!