They are fairly reliable, perform well, and tend to take up less space. For the average modern consumer, they are the ideal products.
Personally, I wouldn't trade my iPad for any other tablet. It's perfect. I've sampled other tablets and the software is just too clunky. Tablets should be simplified computers. I don't want to micromanage my tablet the way I do a PC.
As for my phone, I wish I could get a reliable flip phone like we used to have. I just need to make calls and send texts. Web browsing is a plus but I don't need it. Siri on a old school flip phone would be perfect. I don't need all this other junk on a phone that will break if you breath on it. One tiny speck of water gets on the touch screen and the phone just won't do anything. It's pathetic.
As for computers, idk. PCs are cheap so I have no problem using one until it just stops working. I don't like the fact that on an apple computer, I wouldn't be able to diagnose a problem on my own. Hardware problems are harder to deal with, and I wouldn't know where to begin if I had a software issue. Outside of that, I've no idea if I would enjoy a mac better because I have no reason to buy one.