Perhaps a more balanced look at things is appropriate. That said, we're all entitled to our opinion.
Anyway, here we go. There are reasonable odds that if you play on the north american servers (at least), odds are you feel a little burned by the all the server issues. I, for instance, shirked responsibility for the day and took the entire day off from work to play Diablo 3. Only to encounter 4 service outages where I was unable to play for around 6 hours or so. This didn't exactly make folks happy. Add that to the fact that I'm sure a pretty substantial amount of the population only wanted to play single player mode... well, rage on.
Some of the rage resulted in spam galore on forums, metacritic reviews, probably amazon reviews, you name it. Now, imagine a professional review site utterly destroying their rating of the game with like a 1/10 because of a crappy launch without fairly evaluating the rest of the game. Generally speaking, that's pretty much what the majority of the metacritic user reviews were/are.
Do I personally like the always on requirement? Yes and no. No for obvious reasons. It's completely lame to not be able to play the game in single player because there are some server issues - and quite infuriating. Yes for less impressive reasons. Seamlessly joining friends games, an integrated auction house (you can go on about the cash auction house, but easily being able to sell items that you don't need anymore, etc, for gold, is nice), and reduced (eliminated?) piracy. If I had to pick, one or the other, I'd, of course, take an offline single player mode at the cost of features - and I'd wager most would agree with that.
Anyway, all of that said, the user reviews are mostly just tripe and not worth the time to read. Unless of course D3 is the biggest piece of crap ever released because of a shitty launch. The bottom line here is that any reputable review site isn't going to trash D3 in a full on review because of some day one issues. And if they do, I'd argue that its not a reputable review site.
The primary issue that every single gaming media site fails to mention is that every time the game disconnects, you lose all progress since last checkpoint. Losing 30 minutes of gameplay each time the server hiccups is unacceptable.
Here, I completely agree. Now on the positive site, you don't lose the items or exp... and it is a game that we play and grind through to get items, so in that aspect, its not so bad. But if I'm honest here, yeah - its pretty lousy. I've had more than a few times now where I've had to repeat areas multiple time just because of their server issues. While I'm glad all my items are still there and nothing is lost, I hate having to redo an area. Strange that they have the tech to make sure you don't lose any of your items or exp, but they can't do the same thing with your placement on a map. All of that said, it's annoying but doesn't exactly get me wanting to punch something. Tis the servers dropping that does that for me...
edit - re: the metacritic user reviews - I'm sure there are some balanced reviews hidden in there. But the bottom line is that there is so much rage and rubbish, along with fellow angry folks up voting the garbage, its just not all that useful to look at.