I think the reason for the PowerPoint hate is the homogenization it causes among bad presenters. Let's face it, giving an interesting talk is a skill, and a rare one at that. The ubiquity of PowerPoint makes all of those bad talks very similar, and reinforces many bad habits. Perhaps the difference is that when you had to draw your own overheads, or make your own slides, you were starting from scratch and had to actually think about what you were making. With PowerPoint, you're really just filling in the blanks. It's quicker and easier, to be sure, but that may not necessarily be a good thing.
My pet peeve is presenters who don't preview their slides on a projector. Colors look very different projected than they do on a computer screen. As someone who sits in the back of most lecture halls, the color combinations chosen by so many speakers amazes me. Turns out yellow type on a white background is kind of hard to read.