At first the trickery of the Gibeonites seems to be a serious failing on behalf of the Israelite leadership, and it probably was. The Hivites were one of the tribal groups that God promised to remove from them. Joshua and his leaders didn't consult the Lord before they made their covenant with them and so they were trapped by their own promise.
Was this a good thing? No. The Gibeonites could have easily led Israel into sin and idolotry, and probably did some of the time. Could God do good things through it? Absolutely.
This treaty provided a more obvious tilt in the region's power structures so Gibeon became the flash-point for an epic battle. To their credit, despite complaints from the people, the leaders of Israel refused to go back on their word and God honored them for it. After marching all night to defend their new allies, the Israelite army routed all five attacking armies. Joshua even asked for additional daylight so that he could complete the task--and God answered. There are historical records from around the world that confirm that God did, in fact, stop the movement of the earth. The hail that was recorded in the same battle would have been a natural consequence of the earth standing still, like water sloshing out of a moving bowl that suddenly stops. The kind of celestial even that would be required to stop the earth's spinning on its axis would also have to include a fairly large gravitational or magnetic object in close proximity to the earth, which would also explain the description that God hurled stones at them (a meteorite shower).
Then in his first sweeping campaign that seems to have lasted less than a week, Joshua took a huge swath of the land God had promised them, right through the heart of the territory. The Gibeonites kept their submissive attitude toward the Israelites throughout their history. Later on in II Samuel, God confirms their position alongside Israel, but that is for another day. Ps 15 tells us that a prerequisite for worshipping God is that we keep our promises, even when it hurts. God honors our word because He keeps His own word.
What promises have you kept? What promises do you need to keep?