Um, the revelation that Reapers are actually made from species they harvested is fairly important for them and the trilogy I feel. It's not just "we make them in a factory", it reveals a huge part of them we didn't learn in the first game. And the discovery that the Collectors were Protheans altered and corrupted by the Reapers also adds backstory to them (and sets up the enemy types in ME3). The Reapers not only possess unbeatable spaceships, they also have the ability to corrupt and enslave races they defeat and turn them into unthinking weapons who work for them. That goes a lot further than anything we've seen previously with the dragons teeth (which were thought to be Geth anyway. It's all lore and backstory to the species which I enjoyed and was interested to find out.
ME2 wasn't bungled, ME3 and the entire concept of the game having the reapers fighting us all from the start was the bungle. They had to *significantly* downgrade the power of the reapers to make it work, and it reduced them from an unstoppable force of god to a really, really strong enemy.
Re element of surprise - what do you think anyone could have done if the Reaper fleet just appeared in Batarian space, flew to the citedal, and shut down the relay network? Absolutely nothing at all - they would be totally unstoppable. They had the element of surprise had they just used that relay. Heck, it's more a surprise than a hundred year war involving the Rachnii slowly conquering the galaxy and the citedal, or the Geth doing the same!
