@Artini - you may also want to check that Blend Transparency in the Material Options is ticked (see picture). This is usually the case if you have picture textures but seldom if you use procedurals. If it is not checked, transparency may not give you the result you expect.
TA renders are notoriously very long winded and produce noise also with the highest setting. You can check if it is worth the wait by rendering with a low rays per pixel setting - 4 or 9. The noise will be very prominent but you can judge how the light looks.
There is no true alternative to TA but using a light dome or IBL will often give you very pleasing results. If the Bryce sun is used as main light source, you can disable shadow casting for IBL and speed up the render considerably.