The cross-bars are mainly for "looks." If you read some posts on here, you'll see that the cross-bars may be unsafe for rooftop carriers (due to uplift forces). I personally have them and use them for a rooftop carrier. I have not had any problems with them. You will generally need the cross-bars if you are using a hard-sided carrier. There are soft-sided (bags) carriers out there which do not require the cross-bars. The rooftop carrier is a must for my family's size and duration of our trips... the added cargo capacity is a life-saver. The Ody's room is second-to-none, but we still need more.
They can also be used for bikes, but that is one tall order... and forget about trying to get the bikes that high without scratching your paint.
The wind noise is usually caused by improper installation. If the bars are put on the right way, they should not produce excessive noise. If they do, you can always set them a little farther back on the roof rails. This will usually reduce or eliminate any wind noise.
Remember, you can always order the cross-bars at a later date (like I did). Don't let the sales person pressure you into a buy if you're not sure. Most dealers have them on-hand. It's simply a matter of going there and picking them up.
