I started the iPhone 5 repair without the iSclack. But at the same time I'd purchased a replacement batter for my Macbook Air. When I realized I needed a bigger pentalobe driver for that, I grabbed the iSclack at the same time.
The iSclack made things much less tedious! Besides the hideous glue on the back of the iPhone battery, everything went well.
Two things: I had to read in the comments about heating the back of the iPhone to loosen the glue. That really helped.
Second, whoops, it would have been nice to have more warning about stripping the pentalobes on the iPhone.