"Firmware bugs really cripple the router."1.0 starson by mb822
Pros: Awesome hardware.
Cons: Firmware. This firmware is so buggy, just go to the community support site at Cisco's website, you'll be pretty amazed at some of the simple, yet very crippling, bugs that made it through.
Summary: The hardware specs of this router are awesome. However, the firmware cripples it. There are some pretty fundamental bugs that made it through, which still, after 100+ days since the last update, still affect the router. Go to the community support site and you'll see nothing but silly issues with the router. I've been fortunate that none of the bugs have been show-stoppers for me, but I wouldn't recommend this router with its current firmware (2.0.36 as of the time of this writing).
Cisco switched to a Marvell chipset on the v2, which means that you can't load any solid 3rd-party firmware to address the stock's shortfalls. With this, you would hope that more substantial firmware updates would come through, or at least more often. The routers of some of the others in this price range have undergone quite a few updates which have fixed many issues they experienced. Yet this router, as a flagship of the E-Series, still has a lot of problems.
My final point is that, for some unexplained reason, Cisco has removed functionality that was there in other flagship routers. I'm coming from a WRT610N to this, and I still can't understand how the parental controls are so much weaker than on my previous router. Also, the advanced wireless settings have been removed. In addition to fixing the bugs in the firmware, it's really getting hard to stick with firmware that doesn't feel like it offers any additional value, things like bandwidth monitoring and so forth.
If you're going to go with the e4200, definitely get your hands on the v1 so you can load decent firmware on it. If you get the v2, you'll have buggy firmware, and it doesn't seem like there will ever be a way to get around the lack of updates and fixes, due to the Marvell chipset. It's awesome on paper, and the hardware is there, but being stuck with sub-par firmware is really quite unfortunate.