i have driven my 2012 mustang
gt with an MT-82 for almost 3 years now and has 39,000 miles on it now. i have never had any major issues with the transmission but there are a couple things you could do to make it better.
For the clutch sticking to the floor, you will need to remove the spring assist that is located on the clutch. it is a pain in the *** but well worth it. there are videos on youtube that show you how. the stainless steel braided clutch line is nice to have but does not cure the clutch sticking problem.
secondly for the gear notchiness/grinding from 1-2nd gear and sometimes 2nd-3rd gear issues, that can generally be fixed with a 2 post bracket, if you desire shorter throws in the shifter then you can get a bracket and shifter assembly I.E. MGW or Barton.
The last issue i have personally been having is the high rpm lockout. Some people have had success with installing the whiteline transmission mount. I have not done it myself though, so i cannot comment further on that part. What you could check out is the blowfish racing manual shifter support bracket which everybody that i have read on that have installed this part has said they do not experience the lockout anymore when shifting at high rpm's, plus this part also doubles as a driveshaft loop. I have just ordered this myself and finally hope to be free from this issue.
If you are not looking to race at all, which judging by your post it doesn't seem like you are going to, the only thing i would really worry about doing if i were you is to purchase the 2 post bracket and you should be fine.