Over the past few days I've become increasingly aware that the quality of writing -- and coherence in technological development overall -- would improve dramatically in Star Trek if we simply did away with the concept of FTL sensors. You can't see where you're going at warp, and nobody can see you (though they can see where you're going, following the bright flash that follows you through space). You can't tell what's happening on a planet a lightyear away (though you can see what was happening there a year ago if you have a big enough telescope). You can't track the enemy's fleet from a distance and you can't monitor his transmissions. If you want to know what's going on, you have to send someone over there to find out.
In the end, FTL sensors have effectively become plot holes we've been instructed to accept as canon. Given the choice, I'd rather explain them away as artistic liscense and imagine that "IN REALITY" there's a certain amount of delay going on -- that somewhere in the two and a half seconds between Picard asking Data "Any lifesigns?" and Data answering "None detected, Sir," Picard actually stepped out of the room, got himself a cup of tea and dictated his log entry for the day, only to return to that same spot ten minutes later and have Data report "Sensors have scanned the planet for lifesigns. None detected, Sir." I already
do this whenever Worf hails anybody (and never waits more than two seconds to announce "No response"), so it makes sense that there's a similar amount of cinematic time dilation going on with the sensors.