I haven't really noticed the day/night things yet. But I thought it was cheap last time around. RS is really.. better. It gets rid of that tinny rushed feeling GS had, and feels true to the original.
No new types, as I've seen before....
The Legendary pokemon are harder to catch this time. Ahck!
There's graphical updates.. Like, you can see yourself on the water.. and there's partical effects on the screen like Volcanic Ash and stuff. It's pretty cool. The story is also longer and the whole experience is longer.
Also, you can make your trainer profile and stuff. You also fight reporters, and when you talk to TVs later, you can see the shows! It rules! Another difference is the pokemon boxes in Lanette's PC (someone's PC for a while at the beginning, don't worry, it's not a spoiler in the least) You can actually change the wallpaper in the background. It's cool.
Ah.. the one difference there is, is that you won't be able to link to the previous versions. Well, still, it's like starting fresh and new from the beginning.
Overall, if you liked the previous ones, you'll love these ones a lot.