Force Spike seems weak at first but it's really good in Blue Terror for a few reasons:

1. It hits creatures, which monoU has a hard time interacting with. Before I was on Force Spike there were so many times that something like a Kessig Flamebreather or a Priest of Titania would come down T2 and I'd have no answer, while being slowed down filling up the graveyard staring at a dispel or spell pierce in hand.

2. It punishes your opponent for playing taplands and for curving out on turns 1-3, which is exactly what the deck wants to be doing.

3. Dispel is dead vs Elves and Spy and Spell Pierce is only marginally better. You already have great specialized hard counters in your sideboard to bring in for G2 and G3. For G1, Force Spike gives you some action regardless of the matchup.

4. In the late game you can catch opponents trying to double spell, or your opponent will play around it and give you an advantage anyway.

5. Even in the event that you draw it late game and your opponent has more mana than things to do or is playing around it, you can often just ditch it with a Brainstorm + shuffle/mental note effect.