Compared to eastern states and most states in the west, Colorado is a bowhunter's paradise. The elk herd is by far (by nearly three times) the largest in North America. Other big game are plentiful such as mule deer, white-tail (east CO), black bear, shiras moose, bighorn sheep, and mountain goats. Of course most of these critters require you to win a lottery but there are ample over the counter hunting opportunity for elk, deer, and bear -- especially for residents. The resident license fees are often only 10% as high as nonresidents even though the federal public lands are as much the nonresidents as the residents (but that is another hot topic). YOu'll pay far more for gas if you hunt a lot than you'll pay on license fees as a resident. You'll also be close to some great hunting in neigboring states. The tree stand can come in handy for waterhole or wallow elk hunting. You should plan on learning to call elk and spot and stalk is an important skill for the western hunter. Like others have suggested, the 40-yard shooting question is a very personal decision but becomes more than personal if you do it poorly and give the rest of the bowhunting commmunity a black eye. You should be able to get 15-25 yard shooting opportunities every season and never have to shoot 40 yards. I highly recommend you practice at one and a half to twice the distance you intend to shoot. It is a very rare bowhunter, especially with traditional equipment that should even think about shooting that far. It is also a rare beast that might not change position while that 40-yard arrow is enroute -- resulting in a miss or poor hit. There are some terrific locations to hunt in Colorado besides Denver that will get you to less congested public areas; Montrose, Kremmling, Buffalo Park (above the Rabbit Ears Pass and Steamboat Springs), & Craig.
Finally, if you are leaving bowhunter friends and family back in the east, they are going to expect you to become a Colorado hunting expert in short order so they can come visit in say ....September?