Hello, I would also like to add a couple of points to this endless wishlist:
fully 64-bit app with CPU multithreading support (LDD really IS in desperate need of such enhancements)
add support for trackpad gestures (like pinch to zoom or two-finger swipe to rotate)
allow to put a brick on top of another (would ease solving situations such as placing a car or a minifig onto a flattop brick - as it is it drives me mental all the time) Maybe I'm just a clumsy moron, but I never manage to succeed on this task.
allow to rotate the brick freely in every direction (the free rotation mode could be triggered by a hotkey + mouse, p.e. ALT+mouse movement)
add some kind of tool which would enable to crook the structure by allowing you to adjust the stress of the connection between bricks. In the current release you can't build structures like this, can you? (See picture in code; notice those bent columns build presumably of 3062b's)
http://www.classic-town.net/wp-content/uploads/2010/06/4719103907_dccfbcd144_b.jpg
this tool should also allow to distribute the stress of the connection unevenly (again, see CODE for picture)
http://i47.tinypic.com/104q07c.jpg
add an ability to build angled walls (like this http://www.eurobrick...showtopic=21942) EASILY. It is possible now, but it's a helluva struggle to build them and even bigger to connect them to regularly angled bricks. (I always wanted to build LEGO Pentagon in LDD, unfortunately it is not possible right now)
gravity simulation - to test whether your construction would or wouldn't fall apart if it was made of real world LEGO - handy especially for building builders (I am a very keen LEGO architect myself, so I would very much appreciate the presence of all above mentioned features)
==> basically, allow to connect everything to everything, anyhow and anywhere as long as it would be feasible with real LEGO parts. LEGO is a very versatile construction set, LDD is, on the other hand, incredibly limited. As an architecture builder, I can't build advanced structures without ability to do whatever I want.
generally unimportant stuff:
ability to import custom brick decorations
replace those hideous backgrounds in View mode
better quality thumbnails (when browsing the files in Exploler / Finder)
support for 3rd party cloud storage systems (p.e. dropbox) for backing up / importing LDD files (handy if you use LDD on more than one computer)
+ a bunch of Mac-specific enhancements (oh LEGO, please!)
support for OS X's fullscreen mode
a decent redesign
support for OS X's Versions and Autosave features
add LDD to Mac AppStore (or in case of W8 - windows store)
backup LDD creations to iCloud ?
support for multi-touch gestures (already mentioned above)