Any use the Aeon Collection?

Spectrasonics never runs sales as Bitflipper stated.  I got my Spectrasonics products through Guitar Center with incredible sales coupons to save on the retail pricing.  GC often has 15% off coupons but every once in a while they run a $75 off or $100 off coupon and those apply.  Or you can buy from Sweetwater and do the 3 payment plan to help with the payments.
 
Spectrasonics does do license transfers so sometimes you can find a used copy being sold on KVR forum.  I got my Spec Stylus RMS Expanded that was and saved a HUGE amount off retail price even with a $50 license transfer fee.
 
I would say it's hard to compare Aeon and Omnisphere in a side by side comparision, they can complement each other but one is a synth and one is a sample pack with layered samples and effects you can appy.  kinda different beasts.
 
I often think of Omnisphere as buying a Roland Fantom or a Yamaha Motif hardware synth but cheaper as it's software.  Quality sounds, easy to use and just inspiring.  for cinematic composition Omni plays very well as there area TON of pads and atmospheric sounds.  I have lost so many hours just loading up a sound or going through patches just freaking inspired by quality and the fun only to look at the clock and realize hours had past.  Very few of my VST synths do that, most are just tools and they work or I fight with them and get the sound I want.
 
Aeon is samples with a scripted Kontakt interface and you can apply different scripted effects or the Damage like Punish effects.  the Arp built into the package is easy to use and fun to play with.  There is definatly a character to the sounds though, sometimes you can get a sameness from playin with Aeon.  The character is quality and the production of the interface and documentation is really good.  As with most scripted Kontakt libraries you cannot load in your own sounds your stuck with what is available in the Aeon package but there is so much there and you can multi player the sounds, it's quite robust.  If you listen to the sound demo's of Aeon and you like what you hear - your gunna get that with a lot more under the hood and tweakability - but that is what your getting.
 
I would defiantly check out the Heavyocity AEON collection review by Sounds And Gear on youtube.
https://www.youtube.com/watch?v=6WWXdEeSwi8
it's 18 minutes and really covers a lot of the interface and different sounds, you get a feel for what's there in the AEON collection.
 

I have both Omnisphere and the AEON Collection.    They are entirely different.   But if you are aiming at ambient cinematic style, you cannot go wrong with Omnisphere.   I've had it years, and always discovering new things.   Its incredibly easy to use, yet extraodinarily deep if you want to go that far.   They never have sales, but there is nothing to touch it for value for money.  Without doubt the best bit of software I ever bought.     
 
AEON is much more limited, with only a relatively small number of sounds, and not so easy to edit, nothing like Omnisphere at all.    It does have its own unique sound though, and compliments Omnisphere well.  If you are thinking one over the other though, no contest, you will never regret buying Omnisphere.