On my first playthrough of diamond, I tried training him. I only got him to level 20 before I realized it would take to long for him to catch up with my Level 40 team. I also chose Chimchar, which meant I already had a pokémon with fighting moves.
However, on the playthrough I am working on right now, I am considering training him because my team can use a good fighting/steel type to fill in the 6th slot in my team. It's going to be between him and my Onyx (whom I am Considering evolving into a steelix, I have trained him since after the first gym battle). But, I am probably going to save the metal coat so I can get a Scizor, so it's a tough choice. I think I will try training him with the Vs. Seeker on this playthrough. Maybe I'll trade him into X/Y (if possible) to use later on.