Senate delays and threats, however ineffectual in the long run, can serve to attact media attention and galvanize public opinion around issues where the Commons "opposition" fails to do so. The GST and Free Trade, for example, became much bigger causes celebres because of the Senate's sober second thoughts.
Are you not answering your own question? The Senate is ineffectual in the long run.
The Senate has not served to galvanize anything. In 1988, the Mulroney government was due for an election either way and would have had to face voters very soon on the free trade issue.
In general, I fail to see your point. So what if a bunch of Liberal hack Senators were going to hold up the free trade legislation? In the end, the actual Liberal MPs were lying through their teeth anyway and only served to expand free trade once in government.
You seem to be implying because of the House of Commons is undemorcratic, we need an unelected group of partisans to set the ship straight. I don't think so. All the Senate does is make our system more undemocratic not less.
Let's keep in mind here that in actuality the parliamentary system was functioning quite well when the coalition was formed and the opposition parties moved to defeat the government. It was only an unelected GG that moved to save a PM that should not have been saved in the end by agreeing to the prorogation. And you think this is a positive thing?