Not sure what visa Andreas was on, but when I got mine I had to get an extension every 90 days, which meant going to immigration with papers from my language school and spending 6-8 hours just waiting and waiting basically the whole day to get a stamp. Immigration officers cane to the school to check that we were in attendance twice during that year, and if you were not in class when they came and didn't have a doctor's note, they could deport you.
Another issue is that if you have an education visa in your immigration history, and try to enter on visa exemption soon after you're done with your classes, you might get denied entry, since the education visas have been abused by thousands of agents selling this visa to people who aren't actually studying. The agents claiming that they can get you a "legit" visa from a Bangkok university are just lying to their clients. A legit education visa is for studying, not just getting a stamp and never actually attending classes.
Your border runs won't affect your application. If you get denied, it will be because of insufficient money or that your chosen DTV activity doesn't require 5 years or access, according to the embassy you apply at.
I'm in several forums and haven't seen a single horror story of anyone being denied entry with a DTV.
But I keep seeing comments that there are "a lot of' horror stories out there. Where are they? Or is it the "The immigration officer asked why I was here, so I answered"-stuff that people are talking about?