bperrybap:
1.5x IDE also has some nice features that are not in 1.x
The biggest being that dropdown are now scrollable.
This is critical if you have lots of boards or libraries installed.
Without this capability you may not be able to select the desired board or be able
to pick an example sketch because the entry is below what is on the screen and there
is no way to scroll down to it.
Having this scrolling capability is a MUST HAVE for me as I have close to 100 libraries
and nearly the same number of board selections.
There is a work around in 1.x that I'm using for that, and that is if you install Pauls
teensyduino he modifies the IDE to add in the scrolling menus.
So you can get the scrolling menus on 1.x by simply installing Pauls Teensyduino add on.
There's also the eried enhanced 1.0.5 IDE that supports scrolling menus (I believe this is the code that Paul based some of his Teensyduino enhancements upon.)
http://forum.arduino.cc/index.php?topic=118440.0
Personally, I'd never recommend someone use 1.5.x just for something like scrolling menus. 1.5.x is, after all, still a beta platform, with an unstable code base and feature set. If you want to program a Due, then I guess you don't have much choice. But for anything else, unless you are particularly yearning for adventure, well -- fuggetaboutit!
If someone asks "how do you program a 1284p using Arduino?", the current correct answer is "we have a 1.0.5 compatible core and set of libs".
Well, at least that's the answer I give!
But for the adventurous, I'd suggest a new thread would be appropriate for discussion of any 1.5.x related work on the 1284p core.