- Solid patterns are developing around XMLHttpRequest, including HEAD requests, which may become the ultra-efficient RPC of the web (and not supported by Safari yet). On IE, this requires either an addition to trusted sites, or dropping your pants to the rest of the Internet. Assuming it's possible, an independent implementation of the XMLHttpRequest object in JScript is only a matter of time.
- XPath. This is absolutely essential for navigating DOMs. This can be added to >IE5, which is nice, but you have to bind it to each new document you want to work with, which I can live with if I have to. Safari does not support XPath in any way shape or form.
- E4X, soon. Did I mention how nice this is? Oh yes I did. No more of this:
newRow.appendChild(nameCell); newRow.appendChild(downloadCell); newRow.appendChild(rangeCell); newRow.appendChild(sourceCell); newRow.appendChild(dateCell);...and no more futzing with pasting strings as innerHTML, which is even uglier from half a dozen perspectives. Yes it's faster, yes it's less redundant code, and no I don't like it because it's an ugly, disgusting hack compared to E4X.
(Oh, and: this XPath visualiser by Dimitre Novatchev is very, very nice.)