Always test a rod before you buy it.
Try it out with lines of similar design (head lengths or models) but of different weights. Try at least one line weight lighter than indicated and up to 2 lines heavier than indicated. This will indicate to you which line feels best in your hands. It would be a shame to spend hundreds of dollars on a rod that needs a 8 weight line when what you wanted was a rod that needed a 6 weight line. Any good fly shop should have a selection of lines spooled up to use when testing. Always ask what line is on the rod when you test it, then ask what the differences there are between that line and the one you wish to use. Ask in particular, how this line will affect the rod action compared to the one you normally use.
Want a better approach?
When thinking of buying new gear an angler will usually purchase for fishing in certain conditions. Lets say they want a rod and line combination to use on a larger western river. They want a line that will cut into the wind yet will not be so heavy as to cause undue disturbances on the water. All they have ever used is a standard trout taper on a medium action rod. Thinking a 6 weight, 9 foot rod will do the job they run out and buy a fast action rod based upon marketing or someone elses recommedation. They also buy a new line matched to the weight marked on the rod. Excited to get out and give it a try, they go fishing the next day. All day long they struggle with their casting because they can't feel the rod loading. After a few more outings on the river they get to really dislike this rod becuase it doesn't feel right. Someone mentions overlining the rod, putting a 7 weight line on it. So the angler buys a different line and strings it up. Now they can feel the rod load but the line is now so heavy that it causes more disturbance on the water then they wish and the fish seem to detect the line on the water more than before. This causes more frustration with the gear and the angler really begins to hate the rod.
It sn't the rods fault but more the fault of the process most people go through when purchasing new gear. When buying a new outfit, instead of buying the rod first, I recommend purchasing the line you wish to use prior to purchasing the rod. Put the line on a reel and take it with you when trying out rods. As you will see from the discussions above, and later on in the Taper Design section, it could be easy to make a bad rod weight choice. By testing a rod with the line of choice you avoid purchasing a rod that may be too stiff or soft for your castng style. This saves you the frustration and money involved in having to buy another line that doesn't really fit the fishing. The "feeling" each of us has of a properly loaded rod has much to do with the weight of line and the line taper that is on the rod. Following the advice above, when obtaining new gear will save you money and frustration.