Really Rotten Tomatoes? All you have to say is "An emotional and heartfelt comedy."? I expected more professionalism from all of you. That out of the way, Sideways is indeed an emotional and heartfelt comedy...OK, but it has many other things too, so let's write about them.
First of all, I liked both Giamatti and Church, they have such characters that complete each other. They go through many things in their 7 day trip, and they are so believable and real, that everytime something happens to any of them, we feel it, every tear, every smile, every comedic stuff, everything. Verisimilitude is the correct word to talk about them. They also go through many negative moments too, but those also give the happier moments more strength and power, and also help the comedy to work. It could have gone the easy way putting a lot of slapstick and sex jokes, but they knew what they had in their hands, and they made the best out of it. The sex jokes are genuine and uncomfortable when they are supposed to be, I mean, even the characters in the movie know when it's uncomfortable. Instead of slapstick we get pretty much something closer to real life: just one little crazy thing here, one little discussion here, all keeping the tone through the movie's two hour and seven minute runtime. All these elements hold the movie together and it's just enough to make it an unforgettable experience.
I can hardly think of any problems I had with this movie, so I'll just leave it on "It's a great movie". It is, it's watchable, funny, intelligent and realistic. All the likeable elements and all the joy a movie should have. If you haven't watch it, do it the very first chance you have.