Relativity will bite you on the behind everytime.
The fastest manned ships I see us building will be around 20-30% lightspeed. At those velocities relativistic effects are still quite mild, and it will give the ship's sensors and navigational computers several seconds to locate and avoid any oncoming debris. Unmanned scout and supply ships might be able to reach .5c, but anything faster is doubtful. FTL is a nonstarter as of this point.