I work for an IT company where we each have our share of smart-phones. One thing about the Droid 1 that I didn't like was its lag and delayed response. I've rooted my Droid 1 and OC'd to 800Mhz. Little better, but still noticeable.
Two of my co-workers decide to upgrade Droid devices, to Droid 2 and one Droid X. Playing with the phones they are faster, but still some noticeable hiccups when loading intensive applications, or fast screen switching. These are stock roms.
The fellow with Droid 2 switches to the Samsung Fascinate with the Hummingbird Processor. This phone feels like an Iphone 4 on crack. It's amazing fast, and super quick to the touch. Apps load faster than any of the Motorola devices and the screen has no hiccups - even with streaming music in the background and loading apps. We are all very impressed and this is how a smart-phone should act and feel.
What makes the Motorola different/slower? I don't think it's just the processor/ram alone. Funny thing is that Motorola benchmarks are higher than Samsungs. Which points out that benchmarks aren't everything.