I don't know if this is the most appropriate thing to be saying here since I work for LitterWorks, BUT.... whenever I have the opportunity to talk to a customer over the phone or over email, I always mention the merits of the LM900 (the beige old design) OVER the Mega Elite Models....
For my dollar, I think that the original LM900 is the more reliable model. Although the LM900 doesn't have allot of the same whiz bang features as the Mega Elites ... like an ionic air cleaning doohicky, and a blinking vcr timer clock

I think the LitterWorks Cabinet more than makes up for the ionic air cleaner. Besides, if a timer is all that important, one could just get an Appliance Timer that we all used to use when we went on vacation for super cheap.
One of the arguments I hear about the LitterMaid Mega Elites is that they have a larger litter area... I think that this is a little misleading... CORRECT ME IF I AM WRONG, but I think that the extra area is added by virtue of the Mega Elites having a convex bottom. Yes, this would add a few square inches, but if the LitterMaid is working correctly, the extra depth shouldn't really be all that helpful!
We also have been working with the Litter-Robot folks lately! We really like their system! Again: IMHO, I think the Litter-Robot is very reliable for sure! I like that about it! I think that it's a great choice, BUT the waste storage area is smaller than with a LitterWorks System BUT it's larger than a LitterMaid system. One big positive of the LitterRobot is that you don't need to buy further supplies for it, you can just use a shopping bag! How awesome is that? Really awesome!
Anyways, that's my little ol' 2¢ on this matter!