If you're just at the "considering" stage, definitely go and see him! Old horses are just as wonderful as younger ones. They can require a little more TLC, but it isn't enough to turn them down about.
I got my first horse when he was 20 years old, and he just died last year at 29. I have zero regrets about getting him. He was a teacher and a babysitter. I loved him, and even though I eventually bought a more challenging horse, he was wonderful to have around. He was used for lessons by my instructor, and any friend I brought over could hop on him even if they'd never ridden before. He was wonderful for giving my young horse confidence. He was basically an all around wonderful horse.
He did require joint suppliments, and towards the end of his life we did have to call the vet and dentist out to treat him more often, but he was worth it. Last summer, we lost him and even though it was very sad, I cherish the years I had with him, and I was able to endure his death. I love reliving memories of him, and I love it when my old riding friends bring up the fun times we had with him.
Yes, go look at him and see if he's suitable for what you want to do. Don't let age stop you from seeing what could be a great horse.