I'm using Network Solutions to host one of my domains for the sole reason that they [sometimes] allow me to change my glue records online. However, they keep changing their site and some times they remove the ability to edit glue records. Some times they just randomly turn off the feature and you need to ask them to turn it back on. I believe the link is called "Manage Host Servers". Quite annoying.
Is there a registrar that I can move to that will let me change my glue records without any messing around?
I shifted a number of my domains to joker.com a couple of years back specifically because my previous registrar didn't support IPv6 glue records. I have had no problems with them. Their web interface is pretty bare, but I actually prefer that as I am not fighting through pages of Flash ads just to get to my domain management dashboard ;)
I have hundreds of domains with DirectNIC and have been very happy with their service. They don't cram the up-sells like some registrars do and allow you to edit the glue records through the website without any trouble. The interface is clean and easy to use without all the fluffy garbage that seems to have overrun the more popular registrars. Their normal rate as of this writing is $15/yr for most TLDs, but if you're working in bulk give them a call and they can offer a discounted rate for you that will compete with GoDaddy and the other low-price registrars. In my opinion, they are far superior to Network Solutions in both interface and price. Support has been excellent as well the couple of times I've needed to contact them.