i felt the same way when i started stronglifts; workouts were just too short and too easy. it won't be like that for long. the weight increases for each workout will be noticeable soon enough, and you could probably skip a few weeks if you're familiar with the exercises and comfortable with starting a bit higher.
it's been a while, but if i recall correctly, those early weeks are a time to learn the movements and really focus on form. if you want more of a workout when you're done, do it. pull ups and pushups used to be part of the program, just tacked on at the end...you could just do something like that.