The spec is a bit fuzzy when it comes to HTTP-EQUIV. While it does say:

The META element may be used to specify the default information for a document

and

The following example specifies the character encoding for a document as being ISO-8859-5

<META http-equiv="Content-Type" content="text/html; charset=ISO-8859-5">

It also says:

http-equiv = name CI

This attribute may be used in place of the name attribute. HTTP servers use this attribute to gather information for HTTP response message headers.

Although the only server I'm aware of which actually does this is Russian Apache (you have to have a way of specifing http headers for all media types, so why bother having an HTML specific one?).

I can't find anywhere in the spec that says that user agents that are not servers should pay any attention to HTTP-EQIV whatsoever.

There is also the issue that it is rather difficult to read a document if the character encoding is unknown. If the only way to find out the character encoding is to read the document, then you have a problem.

Real HTTP headers are the way to go, and I'm not aware of any user agent that has a problem with them.