The split image focusing screen is difficult to use in low light or with slow lenses, or extremelylong lenses. If your eye is not exactly centered on the split image finder then it will go dark on the top or bottom of the finder, depending upon whether your eye is above centerline or below. Both annoying and hard to use.
A company called Beattie made intenscreens that were either brighter than the Nikon, or not split image, but just the matte glass screen. Focusing on the matte screen is at first rather hard to get used to, it takes some practice to be able to recognize when the image is in focus, and of coarse your eyes should be checked to make sure they are accurate and wear corrective glasses if necessary. I've know photographers that needed corrective glasses so the focus in the camera was moved a foot forward.
Since 2001 Beattie has been out of business so you may have to find a replacement. There are several companice on the web that may be able to help.
http://www.display-optics.com/products_35mm-format_nikon.htm These guys have # 82110 which looks like a solid matte and #82114 which is a split image finder, but on a 45 degree tilt. this allows you to use the cmaera and lens without as much darkening because of up/down alignment. But then you have to worry about some side to side and up and down. A solid matte in my opinion is best.
http://www.bhphotovideo.com/c/search?Ntt=nikon+f3+beattie+screen&N=0&InitialSearch=yes
Take all this info as a guide, make your own decisions based on tests at a dealer if possible, beware internet claims until you have check them out, get a right of return and warranty in writing if you buy on the internet.
http://www.brightscreen.com/intenscreen.htm