For C/C++:
GTE ignores backslash at the end of line.
Example:
"this is long^#92;
string".
GTE highlights "this is long" correctly,
but "string" is highlighted as plain text.
The same thing is with #define which also
can be backslashed in the same manner.

For HTML:
It's VERY desirable to hidhlight scripts
(VBScript/JavaScript) inside tag
as a script, not as a HTML...

I'd like to see a PHP/HTML plugin.

I'd also like to see the PERL plugin correctly handle multi-line strings.

How about a few more colors to use for syntax coloring?

Syntax highlighting will be revised in the version 4.0

How about making it possible to give different colors to a tag and to it's attributes.

Matlab .m-file syntax?

VHDL93 (.vhd), Verilog (.v) and AHDL (.tdf) syntax?