Well, I'm sorry to say the hype is unwarranted. Spirulina and wheatgrass are certainly good, but not really any better than green vegetables like broccoli and spinach. 1 lb of fresh spirulina or wheatgrass juice is roughly equivalent to 1 lb of fresh broccoli or spinach.
Seriously. You can do the comparison yourself. Go to the USDA Nutrient Database and compare fresh spirulina to fresh broccoli or spinach. Or if you prefer, here's a page that lays out the comparison side-by-side using the USDA's data. Wikipedia also has a helpful table comparing nutrients in wheatgrass juice to broccoli and spinach.
The one area where spirulina really stands out is protein: it's often ~65% high quality protein by weight. No other vegetable could match that, and spirulina "cakes" can be a decent protein supplement for malnourished children suffering from protein deficiency. That's a noble and efficient use for spirulina. But if you're a rich person only consuming 1/2 tsp per day in a smoothie, you're probably wasting your money. Rich people already get enough protein, and 1/2 tsp wouldn't contain enough protein to make a difference anyway.
I suspect the confusion regarding spirulina's nutritional content arose because it's often sold as a dehydrated powder. In that form, 1 lb of spirulina is equivalent to about 9 lbs of broccoli or spinach. But that's not because spirulina is amazing and unique; it's simply due to most of the water content being removed. If we made it a fair game and compared dehydrated broccoli powder to dehydrated spirulina, the score would be even again.
Don't get me wrong. I actually think spirulina is really cool, and I'd love to play around with growing my own someday. I think it'd be a fun project. But let's not kid ourselves about its nutritional content. It's basically the same as broccoli. So if you're buying it at the health food store because it's a "superfood", please be aware that you'll probably get more bang for your buck buying normal green vegetables.