They warned you because you tried to stay long time without a real visa, they told you to get a proper visa. Why should they deny entry if you arrive with a valid visa now? Won't happen if there's nothing else shady in your history.
They are pretty relaxed about it at the moment, but there is no guarantee that they let you in on exemption forever. It's always "up to the discretion of the IO".
How many? Well... at least all who posted it in the visa related groups. I haven't seen even one success story. Exact number? You're kidding, right?
Believe it or not... it's considered mostly as a kind of tourist visa, not as an equivalent to a Non-Immigrant. Anyhow... you are free to search the DTV groups by yourself... please let me know if you can find someone who could open an account with DTV (and without an agent), I'm always open for updated information.
P.S.: If you find any post about DTV and renewal of drivers license... I'm very interested they got two or 5 years. As you mentioned... the DTV is pretty new... so... even the DLT isn't sure yet how to handle it.
Yep, sure thing... but... a residency permit is a complete different thing. Some of the requirements are a Non-Imm-Visa and a consecutive stay for at least three years. So... DTV is definitely not good for that. A "certificate of residency" shouldn't be a problem after the first 90 day report. It's everything a bit tricky now since the DTV is the the first "non Non-Imm-Visa", that allows you to stay more than 60 (90) consecutive days. Also still not clear how the DLT will handle the DTV for renewal of driving licenses... since it's a tourist visa they would give you just two more years, but on the other hand... well, we will see...
The DTV (Destination Thailand Visa) is a Tourist visa, it's neither a work permit nor a residency permit. Many people were rejected, the Banks don't accept the DTV. The main game stopper is the visa... Non-Immigrant is good, a workpermit is more than helpful, everything else is more or less difficult. As you said... it all depends on the branch, so it's still a kind of lottery...