It's the same criticism's found in any other online article about the iPad. Depending on how YOU use it, some have merit and others don't, while others are certainly a negative no matter how you use it.
"It's heavy." Not for how I hold it when I'm on the couch surfing around. I also bought the Apple case/cover for it and it helps in propping up the iPad at certain angles.
"It's slippery." Not for me. The neoprene (or whatever the material is) case gives it a very sure feeling when holding it. And because of how the case is designed, putting it on a table in 'typewriter' mode offers a stable base.
"The screen has too much glare." Not for me while I'm inside my house. As an added bonus, the viewing angle is quite wide. Outside though, the glare is horrendous. Glad I don't go outside with it.
"Forget reading in the sun." Duh. Let's make another paragraph about the same point we just made in the one prior (in the article, that is).
"Fingerprints are annoying." To a degree, yes. However, they only become annoying to me when the screen is black. To sum it up: for a majority of the time I've played with the iPad, fingerprints have not been an issue nor cleaning them off.
"It does not multitask." I don't do many things at once but the one thing I do like to do is listen to music and 'something else'. And the iPad does that and the 'something else' just fine. Even when I have to close an app to open another, the app I just closed still re-opens to where it was.
"The browser is limited." Flash isn't a concern for me. The sites I visit are mainly message forums and news sites. If you go to the iPad page on Apple's website, they have a (growing) list of HTML5 websites and the handful of ones listed cover my news needs just fine and look great to boot.
"The virtual keyboard stinks." Meh. Works fine for me and my hunt-n-peck style typing wife. I don't use the thing to compose documents or emails anyhow.
"No USB port." Yeah, that does kinda suck. It'll be great if the iPad had one and could act as a host and do file exploring, etc. But I can't be upset at something that was never implemented on the iPhone/iPod. I'm not sure where the camera connectivity set comes into play and how that might change things concerning USB though.
"iPhone only apps look terrible." Wouldn't know...only been looking at iPad apps. But common sense should tell you that blowing up an app to over twice its resolution isn't going to leave anyone's jaws dropping. I will say though, compared to iPod apps - holy high sticker prices Batman.
"The price is just too high." There are many arguments one can make for/against the price but ultimately, it's your money.
"It doesn't replace anything." I own a desktop PC, a laptop, Droid and now an iPad. Want to guess what I'm reaching for now when I'm on the couch and want to 'consume some media'? No, the iPad doesn't outright replace anything nor did I expect it too. But it sure beats the pants off using a desktop/laptop/smartphone for the activities that I'm doing.