I think they're still full of great potential in a slightly evolved form. You can get a ton of acceleration out of the interstellar medium, so long as it's dece

I think they're still full of great potential in a slightly evolved form. You can get a ton of acceleration out of the interstellar medium, so long as it's deceleration, and you're not trying to extract all of your energy from random protons in interstellar space. Quickly accelerate a craft up to 0.1C with beamed propulsion, then have it decelerate at the end of its trip with magsails.