It is so a great episode! It has great moments and great scenes...
The story was original. The whole Limbo theme and Yen-Lo, the swords and the fight. It has an adventurous side that really make the episode a good one. That way you don't get bored. Besides, the water story was so original! And the final in the Limbo so original.
The off-screen job was by far the best thing that this episode has... the camera job was really great, the did great scenes (specially in the Limbo set). So, what about that? The sets in this episode were so great! We don't see set like the Limbo a lot in Charmed, I know it is not so realistic, but at least it is very original. It means that they don't do bad endings in the episode. I really really like this set. Besides the whole fight in there was great! And I loved when Piper/Zen is thrown flying to the vortex! It was so great! Some great scenes were, for example, when Piper is in Chinatown and freezes and the blows up! I liked it very much how they did that scene. The scene with Cole and Paige/Phoebe in the hall was great filmed aswell. My fave scene was when Piper got angry and they are in the solarium and Piper starts yelling them because what they did. She's really touched by Prue's death.
The effects in the episode were great (and the camera job helped it!) One of the bigs one was when the whole Limbo changed back! The scene when the vortex changes back too was awesome! with them right there. Anyway, the episode is not so perfect, so scene (I would say Cole/Phoebe fighting scene) were very pointless and they could have been done better. And some moments were weird in the episode. Anyway, the episode is not boring at all and it is very original, tons of action so... what do you want me to say? It has to get a 9! The whole episode was very original, great filmed and especial!