The Swiffer Sweep & Vac does indeed pick up dirt from crevices, and the vacuum does a fine job on crumbs. It's light weight, easy to use, and pretty convenient as well.
If I had a small apartment with hardwood floors, limited space for cleaning supplies, and no kids, it might be appealing to me. If a long-haired cat lived with me, even more so. I live in a good sized house though, and while I do have hardwood floors, I also have kids... which means mud and sticky things that the Swiffer can't tackle.
Without the Swiffer, I have to sweep, pick up the pile with a dustpan, and then mop. With the Swiffer, I have to "Swiffer", then empty the Swiffer and plug it in, then mop.
It doesn't really seem to save me any time to use the Swiffer, it doesn't really do a significantly better job than sweeping either, given that between the broom and the mop I get the stuff in the cracks anyhow, and the Swiffer needs both disposable pads and electricity that the broom doesn't.
I gave it to my mom, who was happy to give it a try. I haven't heard back from her yet, but personally... I don't need a Swiffer Sweep & Vac. [This review was collected as part of a promotion.]