Tore,Web Connection works just fine with Visual Studio 2012 - that's what I use it with only now. And yes - the HTML editor support for intellisense for HTML5 and CSS3 is much better (you might also install WebEssentials which adds a ton of additional support for LESS, script compression, extra CSS editor features like a better color picker etc. and a host of other common things).
You'll probably want to install the latest version of Web Connection as it adds auto-configuration for Visual Studio 2012 (adding the Add-in, Page/Control templtaes, the Web Controls on the toolbar, WCF schema and a few other things). If you're running 5.63 or later use the Web Connection menu's Configure Visual Studio option to update the registration for VS 2012.
As to your post error - I'm not sure. I haven't seen any issues with posts not going through at least not without an error...
+++ Rick ---
On my new laptop I have installed both VS2010 and VS2012. It runs Windows 7 64-bit, and has 16GB RAM. For WC development I have so far used VS2010 with great success. However I want my web pages to conform to HTML5 and CSS3, and have heard that VS2012 has better support for that. But in the documentation for WC i see almost no reference to VS2012, so I have a few questions.
Should I stick to VS2010 for WC development, or should I go for VS2012?
If I go for VS2012, is there anything I must avoid or be careful with?
NB! I tried to send this message a few minutes ago, but it simply disappeared. I clicked the button marked Post Message on top of the message area, and the message area was blank, but I don't think it was sent. This second time I pressed the Post Message below the message area, and the message was sent as it should. In other words, I have reason to believe that the first Post Message doen't behave as expected.
from Maui, Hawaii