I used Sheppard. While not perfect, it did help me score a 93 on the written. I like the way in that it allows you to re-arrange the questions, re-sort the answers, hide the incorrect answers, only study one section, and take practice tests. What I don't like is that many of the "explanations" simply reference a FAR or an AC, which makes understanding some of the questions a real PITA to go lookup.
I used the Dauntless software along with the ASA Test Prep book. I found it good to have the 'figures' in printed form. Dauntless wasn't perfect but it did get me through with a decent enough score (91). YMMV
If you want to get the test over with I would suggest sheppardair. If you want to get in depth and learn about everything, go somewhere else.
22minutes-96% 6hrs of study time with sheppardair. Wham Bam Thank You Maam. Highly suggested.
Don't even think about anything but Sheppardair. They have the most updated questions. Gliem 1300 questions , Sheppard 600 questions. I memorize all the Gliem questions , took 20 practice test all above 85 , made a 68 anic:, threw the Gliem book in the Mississippi river , studied the Sheppard software 2 days , made a 94. Gliem has 7 year old questions.