Just my ha'penceworth...
...On balance, across all sales, the warranty company makes a profit, so the odds are weighted against the honest and average consumer doing well out of the deal. It can be argued that there's value in the reassurance that, if things do go wrong, help will be at hand - but even that doesn't always follow.
Specifically for DELL I've had a bad experience. The item in question was one of their 'free gift' printers for which they recover the cost by charging OTT for cartridges. I'd been planning to bin the printer anyway as soon as the cartridges ran out, but it went bad when the original cartidges still had some life so I tried to claim. emails were completely ignored, phone calls got stranded in a music-on-hold queue, and eventually I gave up and binned the thing prematurely.
Don't get me wrong, I still choose DELL for most new PCs, based on things like quality, value for money, choice, and ease of ordering. But I take thiers, and all other, warranties, with a large pinch of salt.