Its not stressing it at all, It uses practically no resources to accomplish its tasks. The HD is not over worked, and the CPU are more interested in the Main Project then the FreeHAL work units.
If your after tons of Points from BOINC then this is the project to run along side the other projects that offer high points values!
Since early may I have been running the FreeHAL project along side at least 5 other projects with no problems.
Its like a new topping for your favorite pizza, if it doesnt taste right spit it out and never eat it again! If you like it, you might not want to leave like Vaughan And I.