Katakana

Katakana, like hiragana, is indeed worthwhile learning. Often English native speaking students of Japanese make the mistake of half learning katakana or skip learning it all together. Making the assumption that you can get by because most katakana words are English loan words is a big mistake. If you can't read katakana you can be sure that you're not pronouncing katakana words well. If your pronunciation is slightly off you will have trouble being understood.

Learning katakana is not only about "loan words".

Katakana is used for:

Onomatopoeic words
Emphasizing words that would normally be written in Kanji or Hiragana
Foreign names
Terminologies　- words and phrases used in a particular subject or field.

Examples