Pros: Does everything you need: router, firewall, and 3 different kinds of VPN. The SSL VPN is nice because the client software is automatically installed when you login, but it only supports Windows. Tech support replies quickly, and firmware is updated frequently, and the user interface keeps improving. Very solid product.

Cons: You can only have two concurrent SSL VPN users; if you want more, you have to buy an upgrade ($200+). SSL VPN client only supports Windows. The DHCP server does not store the host names in DNS. It does not support UPnP; you need to manually configure port-forwarding.

Other Thoughts: We wanted a firewall that did everything, especially VPN. But we ended up installing OpenVPN on a Linux server, because it was easy to use and configure, cheap, and supported all the operating systems we needed.

But as a firewall and a router, this box has been rock solid for the past 3 years.

Pros: Great product. Very stable and reliable. Overall it is pretty user friendly. Much more user friendly than a Cisco device.

The WAN loadbalancing feature works very well. The site to site VPN service works very well. Eveything I have used it for works very well.

The advanced web/virus filter which is an add-on pays for itself keeing viruses and malware out of your network.

Tons of features in a very inexpensive platform. The entire USG line is amazing.

Cons: Some setup items are a bit counter-intuitive. Definitely not for someone who is unfamiliar with advanced networking even with the GUI. Not really a con, but if you do not understanding networking you will probably not get this device working properly.

Other Thoughts: I found the ZyXEL line and the USG300 in particular when I was looking for a firewall that could load balance outbound connections based on capacity (Comcast and DSL) as well as fail over to backup connection (P2P T1). I was working with Sonicwall to find a device that could do that and they recommended a $10,000 device. We were about to just leave the DSL line inactive (still on contract) until we found this device.

Pros: The Zyxel firewalls have traditionally been well-designed, feature rich and provide and provide more feature/$ than the competition. This firewall (and the other in the USG family which share the same UI) takes this to a new level. It it is difficult to imagine what more it could do. The new UI allows/requires you to define your networks, address collections, interfaces, etc. as named objects that can then be referenced where needed. This is handy for grouping nodes with similar security requirements. You can gather all the devices you want to send mail under a name - say "SMTP_senders". With IPSec, L2TP and SSL VPN you have all the VPN you could ask for and can hook to many sources for credentials. The routing, NAT/adress rewriting features are mind-boggling in their capability (see "Cons" below). I've managed many different brands of enterprise firewall and this one is top of the list.

Cons: Because of their pricing, the Zyxel firewalls are often purchased by folks who aren't full-time networking professionals who then compare them to much simpler devices. I've read reviews here that complain about the complexity. However - for what they do, the previous Zyxel UTM firewalls, do a very good job of presenting their features. The trouble was that there were just a heck of a lot of features. With the USG line, this "problem" is now much worse. From what I understand the USG UI is common across the line. This means someone with a home office who buys a USG100 is going to be faced with a firewall that has so many enterprise features (and a nearly 800 page user guide) that they will be catatonic.

Other Thoughts: In short:
o Great enterprise firewall.
o Without networking expertise you are likely to drown in it.
o I've had great luck with support - though they only operating during business hours, I've yet to wait more that 5 minutes before talking with somebody who knew their stuff.