I guess you know your creation has hit critical mass when you get your own “considered harmful” article. From Gervase Markham’s “IETab Considered Harmful?”:
... its availability also makes the site far less likely to change to support Firefox properly... I'm sure it's very handy for web developers for testing purposes, but is IETab actually working against what the Mozilla community is trying to achieve?
It’s a tool. It’s useful. It lets you view sites in IE’s rendering, in a Firefox tab, if and only if you already have IE on your system. It doesn’t confer any magical abilities, it just eliminates a step or two.
Full disclosure: IE Tab is based on my IE View extension, in the sense that they took my weekend afternoon hack and added the part that I didn’t have the time or inclination to build and support. Which is to say, the hard part.
IE Tab’s a slick piece of work, and people love it for a reason. But just as with IE View, we’d all rather the need went away. Please don’t blame the tools in the meantime.