For customers using K2 smatforms it is not a revelation that IE8 is not something fully supported. In fact IE8 support has been imited to end-user runtime execution only – K2 smartforms runtime, K2 workspace (Home Page, Reports Runtime, Worklist and Single Sign-On) and K2 web parts since K2 smartforms 1.0. And IE8 support was dropped entirely starting from K2 smartforms 4.6.9. It seems to be that it was high time to do so as investments in maintaining compatibility with a piece of software originally released back in March 2009 does not seem to be justified.
Those shops where for one or another reason IE8 is still being used would be interested in freshly published K2 KB entitled “Known issues when running Forms or the Forms Viewer web part in Internet Explorer 8 or IE8 Compatibility mode” which gives detailed overview of issues you may encounter when using latest versions of K2 smartforms (4.6.9, 4.6.10) and IE8.