In the past, there had already been a project by Google employees to port Canvas to IE named ExplorerCanvas (utilizing IE’s older VML technology), but it only worked well with static images, and was much too slow for animations. Google Chrome Frame on the other hand worked really nice during my tests. To give it a look, try running the little test I made and use Internet Explorer (version 6 upwards).
Note that Google’s plug-in, once installed by the user, will not make Canvas simply just work across all sites. First, the developer needs to insert the following meta tag into the head section of their page:
<meta http-equiv="X-UA-Compatible" content="chrome=1" />
Either that, or the user can precede any URL with cf: ... and it basically tells the browser to act like Chrome. You can then use a script bit provided by Google to run the installation. This brings up a (cluttered) installation window (you probably want to set the optional “destination” parameter – I didn’t, and after the installation finished nothing happened and I had to manually refresh – and you may also be able to override the default prompt by configuring the other parameters).
Does this mean developers can now simply use Canvas instead of, say, Flash, for projects where Canvas would be a theoretical fit... without any negative side effects? Not really – because while Flash is deployed on many systems, Google Chrome Frame isn’t, so your Canvas site would thus still bring up a very sub-optimal plug-in installation notice. However, as an additional alternative to Flash for developers trying to make their Canvas app cross-browser, it’s nice to have (ExplorerCanvas in the meantime still makes sense for static vector graphics, because as opposed to Chrome Frame it does not require installation). And who knows, it might even further push Microsoft towards implementing Canvas in IE natively one of these days... just to avoid having developers push a Google plug-in to users.