Sensing someons's Force power

When a Force User senses another force user, do they feel if they are powerful, moderate or weak in the Force, almost like in Dragonball Z, where they sense power levels? I know that Darth Vader said "The Force is strong with this one", but is he sensing the power potential that Luke has within him, or is he merely sensing that Luke can use the Force?

Sometimes they do, but honestly it varies from source to source.

Originally posted by Darth Abonis
When a Force User senses another force user, do they feel if they are powerful, moderate or weak in the Force, almost like in Dragonball Z, where they sense power levels? I know that Darth Vader said "The Force is strong with this one", but is he sensing the power potential that Luke has within him, or is he merely sensing that Luke can use the Force?

They can feel if they are outclassed or if they could destroy the person they're fighting.

You've got it pegged down. The more powerful you are the better you will be able to accurately gauge someone's power.