Runna is amazing at predicting what are capable of if you follow the plan
I have run a couple of half marathons before and have been the occassional on and off runner for a few years but I had never ran faster than a 2:15 half before.
About 12 weeks back I signed up for Runna on a whim to prepare for a Half marathon and Im absolutely hooked now. I just ran a 1:55 Half a few days back and I couldnt beleive it myself. I couldnt even beleive it a week before when I was doing the race pace as part of my training plan and felt so winded after a few KMs and yet on race day I was able to hold it for 21 Kms.
I have followed other free training plans before but Runna gave me the confidence that I could hold a much faster race pace that I thought I could. I also like the seamless integration with watches (coros pace pro in my case) for training calendars and pace alerts during tempo and interval runs. Also the plan updated itself once it noticed I was running faster during my tempo runs and adjusted my race pace acoordingly.
I know most of this can be done through free structured plans and setting up pace alerts on your watch yourself if you have the time and patience but I like the seamless integration with strava and my watch and how much time it saves me from planning everything out. I just signed up for the annual subscription and am now training for a marathon next year.