Since Q2 2010 all new functionalities are listed in the control's Release Notes posted here.

• Added: Rounded corners and shadows
• Improved: Performance optimizations for RadMenu animations in IE (most significant in IE7)

• Bug-fixes

• New Skin - Windows7

• Multi columns enabled with the new pair of properties - RepeatColumns and RepeatDirection (either for DefaultGroupSettings or per-item GroupSettings).
• New Skin - Sitefinity.
• Performance optimizations on the server
• Bug-fixes

• New RadMenuItem property: OuterCssClass - gets or sets the Cascading Style Sheet (CSS) class applied on the outmost item element (<LI>).
• New client-side methods of RadContextMenu - addTargetElement(element), removeTargetElement(element). They are used to dynamically add/remove targets to the context menu.
• Bug-fixes

• Implemented selection support. Added new properties to RadMenu class: EnableSelection - indicates if the currently selected item will be tracked and highlighted, SelectedValue (returns the Value of the selected item or its Text if the value is empty)and SelectedItem. In addition, a server side ClearSelectedItem() and a client side get_selectedItem methods were added.
• Added new properties to RadMenuItem class: Selected, SelectedCssClass and SelectedImageUrl to correspond to the SelectedItem implementation
• The AccessKey property of RadMenuItem is now Localizable

• Full support for Google Chrome v.2
• Compatibility with Visual Studio 2010 Beta 1
• New common skin: Simple
• Added support to render properly in callback / MVC / webservice scenarios
• Bug-fixes

• Full Support for Internet Explorer 8
• Bug-fixes

• Animations are using the jQuery library now
• Added new property UseHttpGet to the WebServiceSettings properties. By default its value is False.

• New property – EnableRootItemScroll. Setting this property to “true” in combination with Width/Height will allow the root items to be scrolled.
• Added new server side methods FindItemByText, FindItemByValue which have a second argument ignoreCase which indicates whether the comparison is case-sensitive (true) or case-insensitive (false).
• Added a new server side method FindItem which has one argument match of type Predicate Generic Delegate. This method can be used to find an Item by some custom criteria.
• Added protected virtual methods for server-side events – OnItemDataBound, OnItemClick, etc.
• Support for server-side expressions (<%= %>) in the ItemTemplate.

• Hierarchical databinding to IEnumerable via the DataFieldID/DataFieldParentID properties
• The group height/width is now auto-adjusted if the menu does not fit the window
• findItemByUrl and findItemByAbsoluteUrl client side methods of RadMenu

• Added ClientChanges property to the RadMenu class. Now client-side changes are available on the server side after postback.
• Added findControl client-side method of RadMenuItem class.

• Added public getter and setter for the clicked flag.
• Added public click() method to the RadMenuItem client-side object.

• Client event arguments now have a domEvent property