Bought the 523 last month, will be on the 3rd one when (if) it gets here. I have wasted about 3 weeks now without it and I had to pay $40 to sent it off for warranty! The third one was supposed to be here today (overnighted) I wasnt going to *****, but I've had it with this company.
I had already sold my other meters to help cover the cost of the Testo, now I'm out $580=Testo, $40S&H, Who knows how much 410A =$$$ now need to buy more tools just to be safe.
The first 3 or 4 pages of the book that came with that 523 went on and on about how accurate and reliable the Testo digital gauge will be compared to the old school ways!
OK things can and will break, but the way they handle their warranty sucks!