Besides facilitating the new adult content policy LL announced recently (which is also the reason this release will be out later than anticipated) the next release of the official client will incorporate features like shadows, flexi prims and bulk permission editing!
"... It is purely meant as an early preview, perhaps to take some nice snapshots, and play around, but it is not meant for any serious work. It is something pre-alpha, it will crash. ...
Included features are:
Bulk permission editing (part of official 1.23 to come)
Enhanced building tools (part of official 1.23 to come)
Double click to wear attachments
Large Prims (only for Opensim grids)
Maximized Network Bandwidth
Worn Inventory Tab
...and a number of more goodies and (hopefully) stability fixes. Too many to mention here ..."