At first, my Yoshimitsu was feeling vey limited, but I'm taking a better grasp of his moves. And I can say as the crowd in Tekken 5 stage: "You can do it!".
After some hard trainings, I think it's very possible to compete with Yoshi on higher level of play. But the timings are more strict, the knowledge must be deep (knowledge about opponents, about arenas and spacing) opponents are more powerful and there are many dangers in using Yoshi's moves. Yoshimitsu's playstyle is "unforgivable", there's little room for mistake, and Yoshimitsu's answers for opponent's mistakes are usually less advantageous than it would be in other character's case.
But this fighting between stronger opponents has a very nice atmosphere included, I can almost feel Yoshimitsu's effort to survive while wielding the weakened sword. It's a feeling I didn't have before, and I enjoy playing him because of it even more (Help Yoshi survive in the cruel world!)
By now I recommend you this forum:
I'm posting there as Kazu-Yoshi-girl. The first posts of stickied threads are a great startup for Yoshi players, very recommended.