Completely normal.

The speed of download can vary a great deal. But in general, you will not be able to download at the full speed of your connection. The clients you are downloading from are almost certainly providing files to a number of other people. As such, you are only getting a proportion of their upload speed. Sometimes you'll be lucky and they will have a fast connection and/or very few other people downloading from them.

More people are trying to download files than are sharing files. This means the competition for shared files is fierce. Quite often when you try to download a file you will be refused because the upload slots are already full.

Mark