Whither election.
By forcing an election over the whole Throne Speech, the opposition will have let the Tories set the agenda for the election. This would play into Harper's hand as Harper thinks his dream majority is only a writ away. By forcing an election on his terms, Harper can then blame the opposition for stopping the bits of the Throne Speech that Canadians might support and then gloss over the bits they wouldn't. On the other hand, if the opposition passes the throne speech and Harper then starts to run the country like he has a majority there is much the opposition can make of this.
First, it throws the Tories off guard. They no longer know when the election is coming. Harper loses control of the timing yet again. Though I'm sure he has election plans for the Speech passing, they're likely to be less certain than a defeat at the Throne Speech. This may cause Harper and the Tories to show their bully face yet again in parliament, as they're not getting their way again. Also, with Harper now threatening every vote to be a confidence matter, he'll again look like the spoiled brat he was during the first few months of his term.
This leads into number two in the things that the opposition can make of this. Time has always been Harper's enemy. Any amount of time that parliament is sitting is Harper's enemy. It's all time for his ministers and more importantly, himself, to look like the childish bullies they were in the last parliament. That act did wonders for the Tories in the polls. It can only help the opposition to drag this out for another couple of months, allowing the good ship Harper to drill more holes in it's own hull.
Another advantage to the opposition for waiting things out a couple of months is the fact that any bounce the Tories would get in the polls for their Throne Speech would die out. Once the "excitement" over the announcements ebbed, the Tories would likely be back down to where they are in the polls now, basically with only their core support. This gives the opposition the control, again taking it from Harper, and we all know how Harper acts when he isn't allowed to control everything.
Finally, and probably most importantly, by passing the Throne Speech and then taking out the government on some bill later on down the road, the opposition gets to pick the issue for the next election, not the Conservative party. This would really be a blow to the Harper Tories as they could find themselves fighting an election on the environment which resonates well with the voter and not the Tories or some pet neo-con initiative that the Tories have covered themselves with and doesn't resonate with the voters at all. All it takes is a little patience on the part of the opposition parties for this to work. It has the big advantage of taking control of the agenda from Harper and gives it to the opposition. This means a greater chance of sending Harper packing across town from 24 Sussex to Stornoway.