If you want to know all the improvements which have been done on the gallery module and how to use the new functionalities, check the [url=http://doc.silverstripe.com/doku.php?id=gallery]documentation[/url].
Great work. Especially the prev/next was missed in the previous versions. It might be worthile noting that upgrading has issues, because of the added functionality. You'll have to go into the properties of each gallery to correct it. The pages are still there, but I lost the association with the gallery directory (and so no pics after upgrading).
There is one piece of functionality I'm missing though. The previous popup window had a link to the original image. Is there a way to bring that one back?
I have some problems with associating a default image with the gallery. If I insert one from the file store, it works well. If I want to replace it with something from the filestore, I get no listing in the drop down list. If I remove it, it is also removed from the filestore and thus the photo gallery. For me, this was unexpected behavior.