Upgraded to 3.0.1 and enabled flexbox, everything is fine, no box, alignment issues etc. Only problem is, if I use wp show posts shortcode, in a newly created page, the images do not display properly, weird though the old pages ( non updated/republished after upgrade) display properly. Have you faced such problem, help appreciated.
nb. It is a 3 column list with Columns gutter 2 em.