Any editor will tell you, one of the most annoying things about editing is waiting for projects to render. If your not familiar with the editing side of things, when you build a graphic, add an effect, or create movement of any kind...the clip has to render before you can truly see what it will look like. The more complex; the longer the render time. And, in addition to having to wait for the render to finish, you can not access any thing in final cut during that time. So that rules out working on another project while your waiting! Although you can still access other programs like motion, livetype, dvd studio pro, and so on. This way at least you can build something while your waiting.
I found a statistic online about the 2007 Michael Bay movie, Transformers, (which by the way was an awesome movie and I highly recommend it!) The statistic said "According to one of the CGI artists at the Industrial Light & Magic studio, the Transformers are composed out of a total of 60,000 pieces. Optimus Prime is composed of 10108 pieces, Megatron is composed of 2411 pieces, and Bumblebee is composed out of 7433 pieces. Ironhide is the bulkiest Transformer in the film, with both his guns composed of 10,000 pieces each"
Now keep in mind, I said that even one little addition to the video cause it to render, and usually for a couple minutes for just a few seconds of an effect. The most impressive stat I found about the movie is "Due to the intricate designs of the Transformers, even the simplest notion of turning a wrist needs 17 visible parts; each of Ironhide's guns are made of ten thousand parts. Bumblebee uses a piece below his faceplate as an eyebrow, pieces in his cheeks swivel to resemble a smile, and all the characters' eyes are designed to dilate and brighten. According to Bay, "The visual effects were so complex it took a staggering 38 hours for ILM to render just one frame of movement;" that meant ILM had to increase their processing facilities. Each rendered piece had to look like real metal, shiny or dull"
That's 38 hours for one FRAME! So I suppose when I think I'm wasting my life away in render time, some people have it worse!