It's kind of interesting to see everyone's opinions on the "correct" amount of description. I've read books by several authors that could technically be considered "published fanfiction", and the amount of description about the world depends on the author. Especially compared to what the reader needs to know. For instance, the book I'm reading now is about gnomes (this is a fantasy book series), and the author doesn't really describe the gnomes physically or their world, except for little details that are important. (Like a character's drooping left eyelid that only straightens when he's telling a lie.)
That's how I really look at description. Unless something is important to know about the character, then I tend to skimp on the description. While editing a fanfic, I found that I didn't detail the color of my character's hair (brown) or eyes (blue) or what she's wearing (a green tee-shirt and khaki cargo pants) because none of that seemed important in the story when I was writing it. I might go back and edit it in if I can find a way to not make it awkward, but eh. I dunno. It does become apparent that my character is wearing cargo pants because she keeps her Poké balls in the lower pocket, but that's really the only description that I included.
My favorite author doesn't describe anything, particularly the characters, because he's not a visual thinker, but that doesn't bother me to not know what the characters look like. I filled in my own imaginings for what the characters look like, and tend to find that I prefer what I decided on how they look compared to what others decided because my imaginings are tailored for me.
I dunno about Pokemon descriptions in a Pokemon fanfics (especially on a forum like this). At least, a super-duper detailed description. Plus, it's have to be more bit-by-bit description and less info-dump.
I personally think that something that is known to probably everybody reading (such as pokemon in pokemon fanfic) shouldn't really have to be explained, at least in detail. I mean, everybody knows how Juniper or Oak looks like, why should I have to explain it again.
Matt's and Ajin's posts are how I feel about describing Pokemon or Digimon or whatever canon creature we're writing about. A writer shouldn't have to give detailed descriptions about what a Pokemon looks like when the creature is first introduced. Usually, the description comes through in the narration. When I say, for instance, that a character's Nidoran twitched his long ears as he listened to her talk, then the reader (who'll tend to have some passing knowledge of Pokemon since they're reading Pokemon fanfiction) will know that this is a male Nidoran we're talking about here because male Nidoran have long ears compared to female counterparts.
Then again, the Nidoran in question is a character that the main character interacts with more, so he'll get more description than, say, Professor Oak because Oak isn't going to be interacted with. It might be mentioned in passing that he's old, but the color of his hair/eyes or what he wears or anything about him won't be mentioned because that's not important.
And not describing Oak much in my story goes back to the fact that my story is Pokemon fanfiction. For example, the novel that I'm reading now about the gnomes doesn't go into detail about gnome culture and what they look like because fans of the series already know that. When it was mentioned in passing that gnomes in the series have exceptionally long names, it didn't have to be detailed because I, and other readers, already knew that. Or there's brief mentions of another race of fantasy creatures that's been seen before in the series, the readers (and therefore fans who have run across these creatures before) know why it's funny to mention cheese in reference to them or why devices run by them tend to fall apart.
Notr everyone has seen what Prof. Oak looks like, koffi~
On the other hand, they have the great wide Internet near them, or they could pick up some clues from the story about Oak. Or, if the way Oak looks is important, then it'll be described later on through the narration as the other character's interact with Oak. (If the writer does do that in narration and doesn't just go "Oak moved from one room to the other" instead of "Oak shuffled into the other room, his bones more tired than they were in his younger days.")
To answer the question posed by Matt, I've found that a lot of things that used to bother me while reading fanfiction don't do so anymore. The standard issue of bad grammar is still there, but it depends on the degree of badness. If it's still readable (and I'm not looking to leave a review to help correct the author of improper grammar), then I'll still read and enjoy the story without a problem. It's the same with a lot of other problems in stories. Ones that would automatically turn me off from reading a story (high school AUs for example) don't bother me so long as the story is enjoyable.
In recent times when I was reading fanfics without the intent to review, the one thing that kept throwing me out of the story because it kept making me angry was just a lack of research. I don't mean just with canon for the fanfic, but tiny things. Like guinea pigs being put into those plastic hamster balls for exercise. That's a giant no-no for guinea pig care, and I was amused when the character who kept putting his pet guinea pigs into plastic hamster balls wondered why all his pets kept dying. I wonder why. The story just had several problems with little details like that, and that's why I stopped reading it despite a lot of people recommending it
and it being one of the few fics that dealt with something in the fandom I liked reading about.
Another thing that bothers me is when there's a clear bias towards making a character's life miserable that logic itself is bent. This same story I just mentioned had a character get in trouble with a teacher at school for something inane because the author wanted to make the character's life bad and wanted to point out that this character gets in trouble at school. Which is okay to point out, but at least have the character get in trouble for actual reasons. Not because the teacher is blind and deaf for not noticing another character punching and taunting the first character.
It's silly petty things like that that bother me while reading fanfics.
A big one that bothers me is the lack of anything new to see in fanfics for a particular fandom, like the Pokemon one for example. After ten years of reading Pokemon fanfics, when you see one original trainer starting in Pallet Town with a Charmander and a rival who's a jerk, you've seen them all.