Hey this is very nice!
I'll second a lot of the suggestions here and also say that the Packed column could be removed as it really isn't useful in this context and will save space (and doesn't apply to some archive types anyway). Possibly Attributes too.
For the header I'd say just make it a bit smaller (the icon is certainly making the whole thing bigger than it needs to be) and then it won't be such a problem if it's static.
Oh, and the Date column should be clear that it's the modified date.