Yes, I have been in this situation as well:

Below is a short video that shows how SlideMagic makes creating logo pages in a presentation really easy. In the first example, I start from scratch with a completely blank page. Notice how logos get plopped in, and how everything lines up instantly in the grid, and how easy it is to add columns, text boxes without having to re-arrange and re-align the entire page. (I have added this slide as a free slide on the template store, you can find it here, stripped of the logos I used because I could not verify copyrights)

The alternative is to start with one of the built-in templates of SlideMagic, search for “logo” in the app and see what slides come up:

Now you can customise the page and swap the logos for the ones you need.

The exact same search available in the online template bank as well (try searching for logo), but users who are downloading the PowerPoint version directly from the web site miss out on the magic of SlideMagic when it comes to manipulating image grids.

My suggested strategy: tweak things in SlideMagic, and export at the very last moment to PowerPoint if you have to share things with your colleagues. You will save a lot of time making those nasty logo grids.