What are some alternatives?
When comparing Crystal and Adblock Fast, you can also consider the following products
BlockBear - Block ads and protect your privacy on iOS with a bear
Adblock Plus - AdBlock Plus is a browser extension for Firefox, Chrome, Opera, and several other popular browsers that prevents intrusive ads like pop-ups and malicious code from appearing on websites you visit.
StopAd PRO - The ultimate ad blocker for Windows and Mac.
Ghostery - Privacy tool for transparency and control
Goodly - Student loan repayment as a employer benefit