They are awesome! Our son was in the infant sling from 8 weeks for walks and jogs on the running track (super smooth surface). We got ours second hand from eBay, bought all the bits (jogger wheel, stroller wheels, sling, extra hitch etc) used it a lot for 3 years (almost everyday, all weathers, off road etc) and sold it for the price we got the main module for.
Having it meant we weren’t beholden to the car for trips to the supermarket, park or tots clubs. When he was older we biked and ran miles and miles together.
Anyway back to the OPs post, I’d just get one. No need to try it out. You won’t regret it.