I paid for a 5D MkII in January, it still hasn't shipped - hopefully in a week or two (another long story increasing my blood pressure).
That doesn't sound right. I can't believe that any legitimate retailer would take 6 months to order one in. Where did you order it from? Are you sure you're not being scammed?
I'm not sure how FF would make the comparative performance of the lenses different, or improve the performance of the 24-105mm. Isn't the crop sensor using the sharpest portion of the lens, thus moving to FF would make it even softer? Not to mention the much higher pixel count would reveal even smaller imperfections in the glass.
Your 450D is trying to get 12.2 megapixels of image information out of the central 40% of the lens' image circle. The 5D Mark I tries to get 12.7 megapixels out of the whole image circle. This means that the 450D requires more than 50% better resolution from the lens to get the same per-pixel resolution. It is true that lenses tend to be sharper in the middle than at the corners, but this will seldom be enough to make the photo from the smaller sensor look better. It's also worth noting that Canon's biggest weakness is in wide angle lenses, and the 450D will of course need a wider lens than a 5D to achieve a given field of view.
By the way, even a 5D Mark II has a somewhat lower pixel density than a 450D, and so will require slightly less average lens resolution to achieve a given level of per pixel sharpness.
I also used Live View AF for the test shots, which if I understand correctly is the most accurate way to focus since it reads sensor data.
I also use that for shooting static subjects, since it's theoretically more reliable. I'll try to do a comparitive shoot with the 85mm F1.8 and the 24-105 if I can find the time over the weekend.