I can't be the only one that finds Xcode's method of "pointing out" where your mistakes are - ridiculous. As helpful and essential as the feature is.. it does not help to make the line I need to fix virtually impossible to read or edit... let alone see...
And don't get me started on the constant struggle to find a "selection" color that is visible, yet retains one's sanity/ability to see what the selected text actually IS!
What am I missing here? I know how to futz with the colors in xCode, I know how to mess with the Appearance "Control Panel", but it all just results in different configurations - of varying aesthetic quality - that are all hard to read... I don't have this issue in TextMate... Is that my answer?
UPDATE: Thanks to the brilliant work, and answer by @amadillu, here is what the remarkably more usable Xcode looks like after installing his Xcode 4 "Fix-Ins"