It plays agonizingly slow for me with a five second delay whenever I try to move. It basically feels like playing minecraft with a 128x128 texture pack when my computer can't even run a 32x32 pack.....
What frames per second do you get?
When you run the game, it makes a client.log. In the beginning is information about what graphics card you have. If you can post that information here then we can also compare it to what you believe you have.
One problem that I've seen with some machines is when they have two graphics cards (like one intel and one nvidia) and Mythruna picks the wrong one to use.
Also, you can try some of the settings to increase speed... in this order:
1) Press F8 to enable low-quality shader mode. This might give you a bump.
2) Press F12 three times to change clip to 64 meters.
3) In the chat bar, type /trees low
4) And as a final resort, you can try in the char bar, typing: /flora low
I haven't really optimized the game yet as I've been working on features first... but those are some things you can try. Maybe things will get better.
