I found that using Zen DNS as a forwarder was considerably quicker than using the root hints, so that's what I do.
Having thought about why this would be faster, I think I see why you have done this. Basically, you're using the assumption that most other Zen customers will be using Zen name servers, and that most other customers will be visiting the same sites as you (Facebook, YouTube, Twitter etc), from the same geographical location (UK, obviously) as yourself. Thus, when the cache expires on your local network resolver, it will forward the request to Zen (very close). Zen will most likely already have a cached result to send back to you from other customers' browsing requests, so you get a fast reply back to your resolver and LAN clients.
Just using a stand alone caching root/hint server setup (like I do), this extra layer of querying is unlikely to be of the same volume so more often than not, when cache does expire for a site, a root/hint resolver will have to go all the way back to the root servers again to return a lookup once more. Granted, this lookup delay is only going to occur once every one to three days (TTL of root servers), but it will happen more often on that setup compared to a DNS forwarding one like you have.
Food for thought I guess. The only thing I don't like about a forwarding setup is that I'm relying on servers I don't have control over. At least I know when something isn't loading (due to DNS), it's more than likely my fault (to have all 13 root servers to be out of service is almost a complete impossibility).
All in all, I would say your setup is probably -the- best possible setup to have in terms of speed, provided Zen's name servers remain 100% reliable. A direct local root/hint resolver would come second.
Edited by mixt (Tue 24-Dec-13 21:18:39)