The speaker, Robin Geuze, discusses the transition from closed source to open source DNS server software at TransIP. He explains the issues they faced during the transition and the steps they took to address them. Some of the issues included buffer overflow, slow DNS propagation, lack of compatibility, and problems with DNS validation. They eventually migrated to PowerDNS and addressed performance issues through load balancing, backend selection, and priority levels for XFR queues. Geuze also emphasizes the benefits of open source software, such as greater flexibility and easier implementation of new record types. Overall, he suggests taking the migration process in smaller steps to minimize mistakes and improve the quality of the DNS setup.