DTAG is bar none the worst ISP to work with. Everything they do is politics, they may decide to 'forget' to increase the bandwidth on a PNI until you take a meeting with german regulators. Almost every other ISP views PNI as the best way to uphold customer satisfaction without breaking the bank over a more expensive IX and will happily add ports when needed, DTAG on the other hand often requires concessions and selective agreements with a lot of strings attached.
I don't think Germans realize just how much DTAG is holding the experience back for end users (given it's partially state-owned)