I might be getting a 90D soon. Could you please let me know what are the pack issues? I am reluctant because I would be owning it well out of warranty for sure.
You will find a lot of mixed views around the 90 packs. Part of this goes to the fact that there were multiple iterations on the 90 pack and I believe there may be some legitimate differences in how the later versions performed compared to the early versions.
The negative comments will state that 90 packs suffered from much higher level of degradation, and at much lower mileage/calendar age than the prior 85 packs. I do not have any personal ownership experience with one of these to give you a first hand, informed input.
I did own a June 2016 produced 90D which I purchased new and owned for 7.5 years. I put right at 80k miles on it before I sold it. You can find that I've posted various graphs of the apparent degradation which I saw, but it was about 8.5-9% overall, with a full 100% charge yielding around 268 rated miles versus the 294 rated miles which Tesla stated when new.
Other comment you will see is around supercharging speeds being severely limited. This is most applicable to the 85 packs. My 90D would actually charge faster after 7.5 years than when it was new, due to a combination of improvements in the superchargers but also software changes which Tesla implemented. My car would still in right conditions hit 150kW peak charging rates versus only 120kW when new. Even with some changes in the charging taper curve, it would still take less time for charge 20-70% or 20-80% than when my car was new.
So I think what you may see will depend heavily on what 90D you are considering. Personally, I'd say away from a late 2015 or early 2016, and look for a mid-2016 (after the first front fascia "refresh"). That I believe will also benefit you from the vintage of the 90D pack, but also some other upgrades/changes which were done with the refresh versus those with the original "classic" black oval nose.
Just my two cents. Good luck on your purchase decision.