I can't say why some people hate adepts, but they sure as frak aren't sub-optimal.
A simple fact is that there are very few niches in this game where being an adept won't make you better then mundane, as pretty much anything a mundane can do, an adept can do it better.
It's pure adepts that are sub-optimal. It's quite easy to grab the low hanging fruit of both the adept and ware trees. Cybered adepts are fine. They tend to be more specialized than mundanes, but better at whatever niche they pick. That's a fair trade-off in most games. But, most people don't want to play cybered adepts. They want to play pure adepts.
Pure adepts run into several issues. The first is that many adepts powers are too expensive for just being simple keeping up with mundanes. The second is that a lot of the cool adept powers are either just nifty (slightly reduced falling damage) or overbalanced (the restriction on melanin control, keratin growth's drain). There's also the fact that it's a common assumption that adepts are the melee character type." Therefore in addition the issues pure adepts have, they also run into the all the issues melee has*. Ultimately you end up seeing a lot of pure adepts who spent a lot of effort on being as good as the street samurai who decided to having a cyberspur would be cool.
Sadly the fix for this is extremely hard. Critias's effort with the Way of the Adept is laudable and a very good start. However you then run into the issue that the good adept power list is quite short. This combined with the fact that powers don't really scale with magic rating means what ultimately happens is PP discounts just let you get the good out of adepts for less. Then you start waring it up. Cybered adepts are just fine, but they get the same power boost from discounted adept powers that pure adepts do.
*- That is not to say you can't make a good meleer in SR. It's just that it's harder from both a character creation and tactical standpoints than most people assume it'll be.