Ever since I purchased the latest version of the it, the HD movies never download shorter then 1 day and keep changing loading time every few mins. I was told by a rep that it cannot handle the HD which is not a good response and I can watch and download HD on my new mac pro...why did I get the lastest apple tv because the rep told me I needed it to be able to mirror my mac on my HDTV only to find out that until the lastest program comes out this fall, it will not mirror. Now I have two generations. But the lasest one takes forever to download.
Whatever the rep told you, it is complete nonsense. There is clearly a problem at your end, the Apple TV 3 is capable of more than the Apple TV 2, and you clearly have the Apple TV 2 working perfectly. Since the Apple TV 2 is able to download from the Internet properly, then my suspicion would be your problem lies on your local network. Interference is a common problem on local networks.
Interference can be caused by other networks in the neighbourhood or from household electrical items.
You can download and install iStumbler (NetStumbler for windows users) to help you see which channels are used by neighbouring networks so that you can avoid them, but iStumbler will not see household items.
Refer to your router manual for instructions on changing your wifi channel or adjusting your multicast rate.
There are other types of problems that can affect networks, but this is by far the most common, hence worth mentioning first. Networks that have inherent issues can be seen to work differently with different versions of the same software. You might also try moving the Apple TV away from other electrical equipment.