Yeah, I can see it from both sides, too. My horse I have now was originally supposed to be a trial-to-lease-to-purchase. She was a "husband horse" for the seller, and the husband wasn't riding her, and then the wife busted her knee and couldn't even keep her in shape for potential use for the husband, so she offered to let me try her out for up to six months, make payments during that time or not, as long as I paid in full by the end of the six months if I decided to keep her. I was thrilled at such a long trial period, as I'm not the type to instantly "click" with a horse (or a person, actually), but need time to grow my fondness for them. But soon after she delivered her, the seller kept asking for at least a commitment to purchase, though I could still take up to the six months to pay, she said. I didn't really like being in the limbo state any better than she did, though, so once I'd tried the horse out on the trails at all three gaits, I went ahead and pulled the trigger and just paid for her in full and got the bill of sale, rather than futzing around with the trial. I never felt a "click" since that implies a sudden clicking into place, but our bond did deepen, but I'd say it still took about 9 months till I really felt that connection. So yeah, a trial has its place, for sure, and I'd love to be able to have one with any future horse purpose (hopefully not for a long time, knock on wood!), but I can see from both the seller AND the buyer side that it has its drawbacks, and it's definitely nice once it's over and a done deal instead of limbo.
Good luck with this mare, whatever happens!