here're some features request (I know, I still didn't tried implicit casting one and I come back with new requests :)) :
1) Aliases : it would be great to be able to declare aliases for classes, methods, members, etc. My use here (but it should also be used for other purposes) would be to preserve backward compatibility between releases (for example, I want to rename a class from cPoint to cCoord whilst preserving compatibily to cPoint class until script writers upgrades their scripts). I know I could declare both classes, but I would then require to declare all members/methods twice. This request is not a high priority yet (as it's possible to make it working using other ways).
2) Variable argument list (va_list like) : my goal here is not necessarily to declare script function with variable arguments (even if it could be great too), but at least to be able to get variable list in C++ code. For example, we could have a string.Printf( ... ) method in the c++ part which would allow to format texts easier in the script part (such as myString.Printf( "value= %d", myValue ).
You can use the collection class in angelscript. Perhaps with a binding of boost::any and some simple list iteration you can emulate va_args. The multiple arguments system in C/C++ is essentially a hack anyway.
The any class may be foiled by having to register explicitly for every type the script uses.