I am, as I have mentioned before, skeptical of Harper's plan to make Senators elected. I am even more skeptical now that I hear he wants to make them elected for 8-year terms. But more than that, I am congenitally skeptical of the whole idea of bicameral legislatures.
Historically, the reason for Canadian bicameralism is clear: the BNA said Canada needed a government similar to that of the UK, and the English Parliament had two houses. The Commons had evolved in opposition to the landed aristocracy, but was mostly powerless until after Cromwell's death. It's main function pre-Cromwell was a chamber to air grievances to the King, while the aristocracy held all the real power. Theoretically, the Commons had to approve all taxes, but there's little evidence of the Commons pressing this power until the 18th century changed the situation dramatically, as the Commons usurped much of the powers of the Sovereign and Lords. By 1867, the Lords was already on the long road to irrelevance.
The bicameralism in the US Congress was directly inspired by the Commons/Lords division in England as well. But that split, and their respective powers, was a direct result of the way the English Civil War ended, and the expansion of Commons' powers with the growth of the Empire. Bizzarely, the American founders saw the makeup of the English Parliament and interpreted a historical compromise between belligerents in a Civil War as if it were a good thing to emulate when drawing up their own constitution. It's as if the Canadian founders, drawing on the experience of the American Civil War, decided to enact our own form of systemic apartheid to keep the peace between Provinces. (An inexact analogy, I admit.)
Probably the most common understanding of bicameralism's virtue today is the one Americans popularized - the idea of the "chamber of sober second thought." This implies one of a few possible arguments for an Upper House:
1) While democratic representatives may make the law, their passions need to be checked by a less-politicized body. This is an argument for an unelected body to interpret the laws and evaluate their quality - a Supreme Court, or Law Lords perhaps - but not for a separate legislature.
2) The legislative process needs to be subject to thoughtful re-evaluation in real time, before the law is signed by the head of state. This is an argument for entrenched "speed bumps" within the Commons, not a separate legislature. For example, a mandatory waiting period - with consequent committee hearings - before the final reading of a bill would serve much the same purpose as a second house. Exceptions could be made for extraordinary circumstances like declarations of war or states of emergency.
3) The structure of the Upper House will simply provide better governance. (Either because of territorial or demographic allotment.) Historically, this is simply ridiculous. More abstractly, if we believed that - for example - the US Senate would produce better law than the House of Representatives, why would we even bother with the Representatives at all? Does anyone want to employ 400+ civil servants who are mediocre even by the standards of Congress?
And all of these arguments assume that we accept the charitable justification for the American Senate, and not the more realistic one - the American founders needed to keep the peace post-revolution, and thus entrenched the power of the slaveowning aristocracy.
Meanwhile, the bicameral structure in the US is positively harmful to democratic governance. It affects the composition of the electoral college and thus the election of the President. (Deleting the senate votes from the 2000 electoral college would have given Gore the Presidency handily.) The Senate cannot initiate money bills, but can stop them. The Senate approves Presidential appointments, something beyond the purview of the Representatives. The examples go on and on - see Sanford Levinson here.
Finally, If we were to make a Senate that were as democratic as the Commons, all we've done is duplicate our lower house - better to simply delete the number of Senators, and add that number to the Commons. Generic arguments for democratic reforms to Parliament generally - for example, proportional representation, or more committee independence - are best employed within a unicameral structure, not a bicameral one.
Canada has been lucky for most of our history to have an undemocratic but effectively irrelevant upper house. In the few areas where the Senate has intervened (GST, NAFTA) it didn't materially change the course of events anyway, for the very reason that Commons - the democratic house - was at fault. Making the Senate relevant, while keeping much of it's undemocratic structure (over- and under-representing various provinces) is most assuredly a step backwards for Canada.