Just uploaded and tried it on one of my yest blogs- still not sure if worth the effort and risk of installing new version was worth it.
Some addition features include a slicker looking log-in page, a built-in spell check ( but you must be using visual editor) as well as an auto save function- this I think is also only available in visual editor ( WYSIWYG) mode. I never use WP in visual editor mode that mode so so far not worth it to me, howver in this new verson, ELLA, you can o tab back and forth between visual editor and code mode. I may actually try this.
Also better image upload management tauted.
The auto-save would be a great feature- I have lost countless posts because I forgot to save. So, will back up some fiels on one of my blog sites before I feel comfortable recommending to clients.
If you are going to do an upgrade to wordpress you MUST back-up your files in case something goes wrong. I tested mine on site I set up just to try out new versions and plugin before I install on blogs that need to work 🙂
It can be a bit tricky to back up and restore your info. There is backup plugin that comes bundled in wordpress 2.0 and higher versions; and here are direction on restoring you wordpress blog, http://codex.wordpress.org/Restoring_Your_Database_From_Backup