What are the effects on usability and task performance in VR systems using linear actuator based ETPHDs?

What are the effects on usability and task performance in VR systems using linear actuator based ETPHDs?

1. When interacting with a virtual environment, is there any significant improvement in user task performance when using the ETPHD over no haptic feedback at all?

2. Given that user task performance is naturally optimal with a real world setup, how does task performance compare when using the ETPHD?

3. How do users rate the usability of the virtual environment, both with and without the ETPHD, compared to the real world setup?