TomasD: I couldn't agree more, these are the same scenarios I use those symbol files. But I don't put them into the _NT_SYMBOL_PATH, because of the synchronous symbol loading (takes more time) - I add them only as necessary (through .sympath+ in WinDbg and via 'Configure symbol paths' in xperfview/wpa).
Driver vendors definitely should provide the symbols! :)
m.g.