Upgrade was very smooth, because I don’t have a lot plugins, however I still go to WordPress Plugin Compatibility Checker to check if I have any incompatible plugins, the list data is not an officially confirmed but still a valuable reference source.
I only have one plugin (TinyMCE Advance) which is not compatible so I disabled it first and click on “upgrade automatically” button. It takes me less than 5 minutes to do all upgrade process, you can say a painless upgrade.
After upgrade to 2.8, I found that there are a new version of Tinymce Advanced V3.2.4, so I did another plugin upgrade and activate it. This is very much simpler and faster than I thought at beginning, I am now pretty happy that I chose WordPress for blogging.