First, the horse seems calm, fairly relaxed, and seems to be giving a good effort to comply.
For a 2007 the horse looks like he is still a bit immature. HE is only 4 years old and seems like he could use some filling out, from the looks of this video I bet he spent his time undersaddle in an arena... He doesn't seem to put much effort into where his feet are as he plods around the arena. I'd put some trail miles on him and teach him that at any moment the gound could slide out from under him (just joking of course).
It does teach them to pick themselves up and pay attention, even if you just lunge them outside!
The rider is doing an ok job but isn't really 'showing' this horse off really well. Thats ust my opinion. In parts of the video her body position seems to hinder this horse and throw him even more on his front end that he already is.
This horse seems over bitted. I would like to see him in a snaffle or bosal... I bet he does not stay so slow so easy.
He is going slow but is not collected, he looks all front end which is VERY clear from his lope. His hind end is hardly putting in any effort.
Depending on how tall this horse is, he has long legs and shorter looking back (from what I can see) I bet he would look nicer at this point moving out as a hunter under saddle.
Do you want a prospect? If so this horse could go either way, I would take a look at his breeding. Pedigree is not a sure thing but its a good piece of the puzzel. I would also like to see conformation shots or go look at him.
Do you want finished? Then walk away, he is not!
Also what is the price of the horse?
While nice this could be my deciding factor becuase while I think he could be a nice prospect I would not pay (say) $10,000.00 for him.