Recently forced to update Macbook Pro (Mid 2012) from Mountain Lion to Yosemite. Performance is awful. Is there any way to change back/downgrade?

Question

(Sorry if this isn't the correct category)
I have always been a fan of Apple and almost always love Firmware updates. OS X 10.9 and 10.10, however, I do not like.
I recently spent a lot of time going through all the troubleshooting steps Apple Support makes you go through before I called them to get my problems fixed as quickly as possible (no point wasting both our time). I had encountered scepticism in the past that maybe my problems were because I was running 10.8 and so to prove that it was in fact a hardware problem, I updated. AppleCare finally agreed to replace my logic board (for a second time) which fixed the performance problems I was having. The process took hours and I ended up being right the entire time.
I originally had my own little reasons for not wanting to update but decided I would try Yosemite since I didn't really have much of a choice at this point. I have now given it a good month and have concluded that this OS version is completely useless to me and near unusable.
A small list of the more annoying problems:
Photoshop crashes and/or needs restarting constantly
my Wacom Tablet doesn't function properly (or at all
my computer lags when I open Dashboard or App Exposé
I get the spinning beach ball for a good five seconds at times almost exclusively when using a feature of my computer such as Finder, Pages, iTunes, etc.
computer feels like it is lacking in specs
Additionally, there are a dozen little things about the way Yosemite behaves and looks that I find hard to ignore. I WOULD ignore these things if my software worked properly.
Yes, I did try reinstalling programs and drivers; no it didn't help.
I paid for a computer running Mountain Lion because I knew I could do my art on it, play the games I wanted, and do word processing the way I liked. Is there any way at all (no matter how long or difficult a process) to downgrade back to 10.8? And specifically without voiding my warranty?
I really don't want to be forced back to buying Windows but I spent a lot of money on something that is now not functioning in a way I can use it ):
TL;DR
had 10.8. needed to update to 10.10 so AppleCare would believe that I had hardware problems. Hardware is now replaced and I need 10.8 back without voiding my warranty.

Answer 1

GrandMasterB wrote:
My problem is the laptop came with Mountain Lion on it and I spent 2.5 DAYS in recovery trying to redownload the OS to install.
snip
That took about an hour and after the recovery finally opened I was prompted with downloading "Lion" instead of "Mountain Lion" I proceeded. It installed overnight. Now my Macbook has Lion on it and the only way to get Mountain Lion back is in the App Store for $20....
This does not make much sense if the Laptop had Mountain Lion on it from new. Internet Recovery downloads the current version of the OS that the machine was built with, are you sure that you did not upgrade to ML from Lion?
If you did you can redownload Mountain Lion for no charge.