Scrutiny?

The UK Parliament has a regular opportunity to quiz the "head" of the Executive branch of government - the Prime Minister. For half an hour each Wednesday when the House of Commons is sitting, Members have the opportunity to put any question to him. This contrasts with the ordinary question times, at the start of business on Mondays to Thursdays, when questions must relate to the relevant departmental minister's responsibilities.

But how much in-depth scrutiny is actually achieved? Judge for yourself. Could "PMQs" be improved? and if so what changes are necessary?