Best viewer/editor for .fem problem in ascii interchange format?

What is the best viewer/editor for working with .fem problem in ascii interchange format?

Preferably one that supports tree-browsing of the XML parts of the .fem file!

I have been playing around with the following (none of which support XML browsing):
[list]
[li][b]Context:[/b] Nice features and an overall good performance (best overall so far)[/li]
[li][b]firstobjectXML Editor:[/b] Free and with great performance[/li]
[li][b]Notepad++:[/b] chokes up so I would not recommed it[/li]
[li][b]gVim:[/b] can handle the files but its a bit sluggish[/li]
[li][b]TextPad:[/b] is OK but costs $[/li]
[/list]

I used Context, which is faster than a simple notepad. What is the advantage of firstobjectXML ? It doesn't look make for manipulate ascii, isn't it ?

Thx for the excelent suggestion:

The main advantages of using firstobjectXML is mainly performance when dealing with large files and its free :)

It still dosen't enable "XML browsing" of the XML parts of the files which would be nice.

I have given Context a whirl and from what I see I like it.

It has a lot more basic features than firstobjectXML :)

I have updated the small list to contain Context aswell