i've give you both sides, first on the portable side
i have galaxy s3/iphone touch
netbook
kindle
(newest) kindle (wifes)
ipad
i'm inclined to say that i use the ipad for games/browsing/hulu whatever... and if i want/need to read a book/pdf document i will use the kindle (it also has text to speech so if i'm lazy i can do that)
the reason why i do that is cuz it's easier on the eyes, cuz of E-Ink, this will be readily apparent if you want to read outside, i was able to read a book on the beach with the kindle, the ipad with my mifi and a sun umbrella, just did not work too much glare.
my wife is the opposite, even tho she has access 2 kindles she never takes it since she has the ipad, for her it's about convenience, and that means carrying one less item, and that one less item is handled by carrying around the ipad.
i like to take the netbook with me to bed, while i leave my laptop in the kitchen, in short i like my devices to do separate functions, my wife likes the ipad to do everything.
i think the main thing is if you REALLY want a reading experience like a REAL book, then get an e-book reader, it'll be easier on your eyes, you have to try em out in store.
plus they are so cheap now i mean i've other e-readers in the past they cost a boatload, and were "ok"
the new kindles and kobo's are pretty awesome now.
i will say that the 6in screen of a kindle feels, limiting i mean i'm coming from a near 5in phone, and using regularly a 10in netbook or 10in ipad, imo 6in is just fine for reading e-books, but not for any kind of graphics, i'd have to use a 10in screen for that.
but everything you want to do, you can do on an ipad, they even have all the apps for it, comic readers and flipboard come to mind.