Red Superfly
You creepy little stalker
Well, seeing Sidious fight will help solidify both Vader and Luke as ass kickers later on.
Put it this way, the Emperor was worried Luke could destroy both him and Vader. Vader also defeated Sidious and Luke withstood a barrage of Force Lightning from him. Now when we see this guy pretty much hand Yoda his ass on a plate, it will show how Luke and Vader compare respectively.
To be honest, I was hoping the inevitable Palps vs Yoda confrontation would have been Force only. I also wish this was the ONLY time we got to see Yoda fight. I hate the fact that we've already seen Yoda fight in Episode II, which was detrimental to all characters involved (made Dooku, Obi and ANi look like 3 complete tools when Yoda did his fanboy dance). They should have saved Yoda's skills for III and III alone, to be honest.
It would have been really better if we DIDN'T know Yoda was a saber user. Sidious confronts him, attacks him, and in complete defense Yoda pulls out his saber. That at least would have been special.
But, we know Yoda and Sidious are gonna do the whole square-off thing again. Pretty mundane. I'm sure the fight will be brilliant eye candy, but I do wish they settled it with JUST The Force, but, oh well.
I always pictured Vader as the "hands" and Emperor as the "brain". The fact Sidious wields a lightsaber with greater force than Vader himself will prove to make Vader a bit redundant, which I fear most of all for the saga. This fight has to be done carefully as to not to harm the entire series.