Yes, it is possible to use your own name server.
One thing to keep in mind is that there we will be able to offer little but general advice in the way of tech support for DNS issues when we have no control of or access to the DNS servers that are authoritative for your domain name.
There is also the possibility that we may need to make internal changes that could result in a little bit of downtime if we aren't in control of your DNS. IP changes or site moves fall into this category, but doing these things without you first requesting them is rare.
If you're comfortable doing your own DNS, then it is fine by us.