I LOVE my 17 HH horse. She's just SO much to love. And her big drafty trot is wonderful. I can indeed mount her from the ground (I'm 5'4") -but HECK if I look funny doing it! Haul leg up, hop a few times, scramble up. I've not yet tried it with my new saddle, which doesn't have a saddle horn... so I'll have to see how that goes.
I might be alone here but I absolutely love big horses. It's a lot of horse to handle, they eat more, you need a bigger trailer, yes - but riding them is fantastic.
Go check the horse out. See if you like him. Bring an UNBIASED friend who can tell you any faults, and try to decide without any emotion pushing the decision making process. And good luck, he's a GORGEOUS horse :)