They'll repair a broken screen, replace a faulty digitizer or camera, fix Streaks with liquid damage, resolve audio and charging problems, and fix headphone jacks, proximity sensors, and GSM/WiFi issues. They'll also replace a dead battery (I would hope that you could do this yourself!), patch up a busted mainboard, and even install Android updates. I'm not sure whether this last service includes rooting and installing custom ROMs, but it costs £25, which is outrageous if it's just an official OTA update. The company also seems willing to fix other problems not mentioned above—you can contact them for a quote—and offers a 12-month warranty on repairs. Turnaround time is quick too.
So although some of the prices are high (especially for international customers), they seem like a good place to turn to when your warranty doesn't cover whatever just happened to your Streak.[Dell Streak Repairs] Thanks to everyone who sent this in!