I upgraded to 2.7 RC 1 after it was stated that, "We think RC1 is ready for everyone to try " Unfortunately there is one obvious bug that has been missed. When you are on the dashborad and click post> add new > visual tab no icons display (e.g. no bold, underline, internal links, ect) except for adding media. Then if you select a post > edit it brings across the post to the HTML view and once you click on visual no text is displayed.
I hope that this obvious error is corrected prior to the final release of 2.7.