Just read this chapter.

Ikkaku is badass, i love his fighting style.

I kind of think that his shikai can do more than just becoming a spear, maybe he wasn't strong enough to learn about it's power. I mean Ichigo's blade was in shikai from the start but it took him a while to learn about it's power, shooting that beam thingy. A Zanpakutou can be released without using it's power.