For me the Laboratory software is pretty much useless because it gives me much more flexibilaty to use the original synths inside an Instrument Rack in Ableton.
I can load a Simpler or Sampler to use the Rex files and even my own loops. I can split into more different sections, add fades, layer more sounds, pitch up or down, create MIDI automation for volume, panorama and all the other parameters and and and.
I don't have to recreat presets because of the "Loaded by Laboratory" bar and I can use other soft-synths in addition. There are so many reasons why I know that the Laboratory is not that powerful I thought when buying it, even if it's theoretically usable on stage in standalone mode. I guess that it will never fit my needs as a musician if there will be no REX and MIDI import and the LBL-bar is going to be removed.
There are many many other posibilyties that I don't have using the Laboratory but with Abletons Instrument Racks.