Blizzard just announced that soon they will be retiring the MoP Digital Deluxe. If you haven't collected the Lucky Quilen Cub yet, you'll want to do it soon. March 10 is the cut off for the Digital Deluxe; after that you'll need to find an unused Collector's Edition of MoP if you want the pet.
I haven't heard of any Pet Battle strategy that requires the Quilen Cub, but the pet is unique in its model and idle animation at least. :)
For me, I would collect it but I'm still bummed about not having all of the CE pets. Since I'll realistically never collect the original vanilla CE pets, I decided that I just won't collect any of them. Keep in mind that this mindset was determined prior to Digital Deluxes being a thing, and CEs were out of my price-range.
All of this is likely to change with the release of WoD and the Dread Hatchling. I have a soft spot for the little guy since its bigger counterpart, the Raven Lord, played a major role in my druid-y past. I even went out and collected the raven mount just so I could see if the pet and original Raven Lord mount interacted with each other. It looks like they've amended the spell to be triggered by both the original mount and the new raven mount, though.
I'm pretty set on purchasing the Digital Deluxe of WoD, but that leaves me with a dilemma. Since I'm breaking my "rule" of not collecting CE pets, should I just go for the Lucky Quilen Cub as well? Perhaps I can make an exception for only Digital Deluxe versions? I only have one week to decide, so I better make up my mind before then!