After four months, the biggest mistake I made was not buying them when I first tried them for work. I can't think of a tool I bought in the last year that has saved me so much time.
Have you used the older TT-65 tweezers? I found one at a hamfest for a really good price and am looking forward to using it.
I was using these for many years up until now. There are a few problems for me which is why I bought the new set. First, it's like holding two P90 irons in one hand. They are big, bulky and get hot in your hand. They can throw out enough heat to to remove/solder about anything but I was using them more and more for smaller surface mount parts. I bought some finer tips for them which helped some but every time I used the smaller ones at work, I was reminded just how bad they were for the work I am doing. I also only have the one ST45 station, so I had to swap the cables. Even for my hobby work, this was a bit of a pain.
So, very reliable, lots of tips available, pull large ICs without a heat gun.
The MT-100 with the ST50 heats up fast. Seconds. It's so fast to heat, I just turn it off as soon as I am done. The TT-65, well, it takes as long as my P90.
With the MT-100, I can get into places I would have never attempted with the TT-65. I have a lot more hand control with the MT-100 than I ever did with the TT-65.
I'll keep the TT-65 in case I need to do some large part again.