I wish people would spell check more often, the odd typo is fine, but when there are loads it's off putting.
I wish writers would finish the story (or couple of stories) they have going on before starting another. It's frustrating to see loads of unfinished stories by the same author and puts me off reading as I know they aren't going to update.
I wish people wouldn't write really long summaries which include parts of the chapters from the story. Keep it simple.
Although I do like a good romance, I wish there were more action/adventure/sci-fi/AU group stories out there. There are some great ones at the moment, but I'm greedy, lol.