I'll need to read up on this a bit more. It does appear to be significantly more economical to stay with DNS/ME.
http://www.allthingsdistributed.com/2010/12/dns_amazon_route...
http://help.godaddy.com/article/4041
Disclaimer: I don't know/care about support since my site is non-critical but Godaddy promises premium service coming soon. My site is running smoothly serving 10+ mil. pageviews per month. Time using Godaddy's DNS until now: 3 months
Slicehost doesn't charge you anything for DNS hosting if you use them for some kind of VPS hosting. We use their DNS for our (dev and staging) servers that aren't even hosted on Slicehost and it doesn't seem to be a problem. It's the one reason why we continue to keep a few of our VPS servers hosted there since competitors such as Linode are so much cheaper now.