I don't know if you read books or anything on your devices, but I've found that reading on an iPad Air to be *significantly* better than my previous devices.
I don't own a tablet - I use a desktop machine for every day work, a laptop around the house and an Android smartphone. I wouldn't really want to read books on my smartphone except in an emergency - screen's too small to be comfortable. And I don't want a bigger smart phone because then it wouldn't be convenient to carry around and I honestly can't think how a higher resolution display would make my phone better.
On the other hand, my wife does have a tablet... She occasionally reads books on it, but it mostly gets used for facebook, web surfing, photo browsing, etc. My experience of using it for reading books isn't great - if I want to sit in the garden in the sun I find the screen too reflective, and if I want to sit in bed at night then a backlit screen is really glaring.
I think, if I were going to buy a device to be an ebook reader, I would have to buy an epaper device to be really comfortable with it, and epaper is a bit too limited to use the device for non-book uses. So since I can't get a device that would be a reasonable all-rounder then I'm not likely to buy one soon. The perfect tablet for me would probably be one that has an LCD display on one side and an ePaper display on the other so I could just turn it over to choose which display was most suitable for the current situation - no one makes such a thing.
In truth, the prevalence of DRM on ebooks is likely to keep me from being especially interested in buying an ebook reader. Whilst I do consider tablets to be quite "shiny" and nice for surfing the web on, when I look at what I'd use it for honestly, I really don't think I'd get a lot of use out of it so there's not a lot of point in me buying one.