I like the design of stuff in this mod, the structural parts are a nice bonus for making cool ships, more structural parts is always better. Command pods look great , they are better than stock but not OP. The different fuel tanks are good for making more beautiful craft. The solar panels are well designed, for stock craft they are completely OP though, they generate on average 20 times more energy than stock solar panels for equal mass. I like them anyway because they are balanced and actually required in combination with argon and xenon engines in some other mods.
However, some stuff is really too overpowered for them to be enjoyed by anyone who plays ksp for the challenge, most people.
That LAE250 engine is a thruster/RCS block in size and weight but has thrust and lsp equal to engines for heavy lifting.
The electric and fuel generators are exactly like using the infinite fuel and electricity cheats. "Requires 24/min electric charge - output 26,5/sec electric charge" "Requires 24/min electric charge - output 420 liquid fuel/sec & 420 oxidizer/sec & 260/sec monopropellant"
$300 stayputnik + $75 solar panel + $70 empty oscar fuel tank + your generators + your LAE engine = $7.595 / 1,5 ton / 13.5TWR craft with infinite fuel & electricity. I don't think anyone wants to land on every planet and moon in the universe for $7.595 on a single launch