I've owned a web hosting business for a decade (hobby) and worked in the hosting industry for 13 years. I manage hundreds of domains on my personal name servers and at the turn of the century, I managed 500,000 zones on my employers DNS servers. I still work in the hosting industry and I also maintain a side business that consults with both large and small ISPs and web hosts. I regularly work with registrars and consult for clients of registrars.
In all of my experience, I've only run across two registrars I'd highly recommend. I use eNom and couldn't be more pleased. Many of my clients use eNom as does my current employer and I've never heard an ill word against them. The other registrar I'd recommend is Tucows/OpenSRS. My clients who use them are rabid fans, something you just won't ever hear from a GoDaddy client.