I find myself taking Exceptional Attribute on many of my characters. The die pool is often determined by stat + skill, and it seems to be more effective to start out with a maxed-out stat and a few maxed skills in my area of specialization, even if that makes me have to buy up several other skills during play.
The attribute you choose, of course, depends on the character type. There's the (elven) face with a Charisma of 9, the decker with a Logic of 9 (6 + 1 Exceptional Attribute + 2 Cerebral Booster), the bodyguard with an Intuition of 7...all of these allow you to have your area of specialty at 13+ dice even before adding 'ware, and getting close to 20 dice after all your other bonuses are added in. This also lets you get anything related to your prime state at a decent level for a mere 2 Karma expenditure. Maybe your face is a smooth talker and doesn't like playing the heavy...but with a 9 Charisma, you can get Intimidation to 10 dice easily, and higher if some of your general bonuses carry over.
Perhaps the most extreme example is my daughter's character, a physical adept who just completed her first initiation and now has a 12 Agility. She's sitting on 21 dice with her main weapons (6 skill + specialization + laser sight/smartgun), but could pick up any weapon and use it at 11 dice, or 13 dice once she has a chance to spend a few Karma. Sure, it makes her a bit of a pro from Dover, but the sacrifice to her other abilities isn't as high as you might expect. For example, she still manages to squeeze out 12 dice for Negotiation (Bargaining), so she's more than just a weapons specialist.