Yes - knowing my pace makes my harder workouts more accurate (especially important to keep my initial pace in check and overall pace consistent)
- I like tracking heartrate and often use this metric to pace tempo runs
- overall mileage tracking is fun for me
No - I have to fight the urge to avoid being hyper-focused on pace for slower/recovery runs

I use an older fenix 2 + HR strap...kept the initial buy-in cost low and they work great.