It is very important because it grants the unity skill that lets you revive your squad members if they are injured in combat. You will get an ability to develop this talent at one of the crucial plot moments. Like in case of decryption/electronic, you should always have in your squad someone who has first aid at high level so he could cure all its members (this talent is used when you press Y to use med-kit). Hint! You don't have to improve Shepard's decryption/electronics as long as you take with you character who could handle security at high difficulty level (e.g. Without them you couldn't complete or even get certain quests. You should develop them as soon as possible so you could open locks and containers and decrypt information hidden in terminals. These talents are almost that important as charm/intimidate.
