It's also worth pointing out that a Beta is usually considered to be very close to the functionality of the final product
Usually, perhaps, but not apparently at Microsoft - at least in the case of IE7. The current beta version may be close to the look and feel of the final interface, but judging by the comments on the
IE developers' blog they intend to a add a lot more features and bug-fixes in areas like CSS support.
That's why I'm not losing any sleep over the IE7 beta, and I recommend you don't either. Its a beta. Unfinished, unreleased, likely to fall over in a heap - that's what theyre like. Heck, we spend enough time working around bugs in MS's finished products without worrying about their unfinished ones! FWIW, my understanding is that the current beta has much the same (lack of) CSS feature support as IE6, so if your site looks OK in IE6, it'll probably look the same in IE7beta.
Now, if you're worried about how your site will look in the full, released version of IE7 whenever it comes out, that's a whole different kettle of fish (though it's not the question you asked). Apparently it will fully support CSS2 selectors, so you're right - you won't be able to use the child selector to pick out only non-IE browsers. But the question is, why are you trying to identify browsers at all? Here are some possible scenarios...
[ol]
[li]The rule contains something that IE5-6 can't cope with, modern browsers can, and IE7 can handle too. E.g. PNG transparency - You can carry on using child selectors as before, since IE7 can understand the "non-IE" rules
[/li]
[li]The rule contains something that IE7 still can't handle - You're gonna have to find another way around this one (see below), but we can't know how much might fall into this category until the final product (or something very close to it) is released.
[/li]
[li]You just want to send something to (or hide something from) IE for some other reason, regardless of the version. Eg. a "Get Firefox" ad

. This is probably the least likely case, and can be dealt with as the previous one.[/li]
[/ol]
So how will we pick out IE7? Two possibilities - either use a new hack in your CSS (no doubt somebody will find one once they've got a final version to play with), or use IE's conditional comments feature to target a stylesheet specifically at IE. I'd probably do the latter, at least in type (3) cases. You could also use some server-side browser sniffing if you were desperate.
How to manage multiple CSS hacks for multiple browsers across your stylesheets? Take a look at this article:
. I've not implemented it on my own (fairly simple) sites, but it seems like good advice on larger projects.
-- Chris Hunt
Webmaster & Tragedian
Extra Connections Ltd