About to buy a 5G SH-AWD. I have PTSD from 3G tranny issues (twice). Am I safe?
 

Test drive it and make you you can live with the way it shifts (especially downshifts when accelerating after slowing down). Also make sure to drive it on the freeway at 70mph to see if you cal also live with the shimmy / vibration etc.

I never had any 3G tranny issue, but I would avoid the 15 TLX like the plague. And honestly while many say the 16 was better I honestly think they have had a continual improvement in the TLS ZF and I am not sure I would do the 16 either even with many people swearing it was better.

Have you driven a 5G? Coming from the 3G tranny the ZF will feel laggy and sluggish and while you will likely get used to it I could not see myself committing to owning this car with the current ZF. While my 19 is far better than my 15 was it still struggles at rolling stop situations where you then accelerate again, the downshift and shift back up feel like an eternity at times and there are still times where you want to make the sudden quick turn to take your spot where the tranny is still far to slow to react.

I took a ride in a co-worker's 2007 TL a few weeks ago and boy did the good old days feeling rush back, that car handled and with the 6AT was sweet and holds its own even today.

Find a way to drive one for a day or 2 and then decide.

I have owned 3G TLs, 4G TLs and a TSX V6 somewhere in between and I had very positive experiences with all those models. Based on my history with Acura, I wanted to stay with them. I have followed the TLX since its debut in August of 2014 as a '15 model. I have read numerous reviews from journalists and owners alike. All of my research had me quite concerned about making the jump from TL to TLX. I did however resolve not to buy a '15. I found a '16 that I liked and went and test drove it. After the test drive my fears were mostly, if not completely abated. I've owned it now almost 2 months and I couldn't be happier with it. I will concede that the transmission is a bit lazy but I don't find it intolerable in any way. I'm in no way discounting the issues people have had with their TLXs but not every TLX has the issues. The transmission in my '16 is pretty smooth shifting, albeit a bit slow at times, but again nothing intolerable. I do not have the vibration issue at all. The car is comfortable and I have really enjoyed it so far. I plan to write a review soon comparing it to my '13 TL. My point is that you need to test drive the one you're interested in and see if you like it or not. That's really the only way you're going to know. If I had made my decision on comments I read online, I probably wouldn't have purchase the car that I'm now really enjoying. Good luck to you with whatever you choose.

Save up for a 2018. JMO.

There are different ways to answer this :

1) If by "safe" you mean "safe from the transmission failing". There hasn't been a trend of transmission failures in the TLX although there were some failures noted in this forum in the early ones. That being said, the later the model, the better it seems with the TLX. I'd stay away from the 2015's.
2) If by "safe" you mean "safe from oddball or wonky shifts due to the transmission", definitely stay away from the 2015's, but there have been models beyond that where people have mentioned they didn't like the shifting. I've driven a '16 as a loaner once and thought it was light-years better than the 2015's, but others have still complained about not like the shifting.

TL Type S
 

Now you're talking about 2G TL issues. Those 5-speed automatics were pure trash and thankfully Hondacura learned from them. The 3G TL described by the OP had a better transmission (though he got really, really unlucky!), and the TLX has different issues centering primarily around shifting issues rather than outright failures.

The 3G problems depended upon the year. The 07 and 08 transmission were much better than previous 3Gs.
My 2G (1999) had two transmission failures but my 07 has almost 300,000 miles and runs great.

I personally would not buy a ZF9. I found the lag to be so frustrating and I would not trust for the long term.

why punish yourself with a '15????