Alrighty, here we go:
1) What is your blogger name and URL?
Kknight at http://keystor.blogspot.com
2) How did you learn about the circles?
I came across the book Rapid Chess Improvement at Barnes & Noble while browsing the chess section.
3) When did you learn about the circles?
Around December of 2005 or January of 2006
4) How long have you been going through the circles or how long did it take if you are finished?
I did my first set of circles in 2 months or so using Chess Tactics for Beginners. I did 20+ circles with that collection (including reviews since.) I've also done a similar number of circles using Advanced Chess School and again using the first 3 tactics modules of Personal Chess Trainer. I can now sit down with any one of those collections and burn through the 1,000+ problems involved in an hour and a half to two hours...less for the 720 problems in each of the PCT modules. Combining those collections gives me a total of over 4,000 problems that I have "circled" through.
5) How is your progress?
Online, I improved by ~500 ELO in a year on Playchess.com...from about 1400 to about 1900. Live, I had a performance improvement of over 500 between two tournaments a year apart. In the first I ended with a PR of 997. A year later at the same tournament, I ended with a PR of 1502.
6) Does working with the circles alone work for chess improvement, or is it more helpful to join the Knights?
I'd say joining the Knights Errant is beneficial because of the accountability and sense of community that it provides...but that certainly doesn't mean that you can't do it on your own. I joined the Knights after completing my circles with CTB, Adv. Chess School and Modules 1 & 2 of PCT on my own. I did Module 3 of PCT during my time with the Knights.
7) Are you a scholastic player?
Nope...I'm a 28-year-old working adult with a young family. The oldest of my two boys plays chess occasionally though...he's seven years old.
8) Would you recommend the circles to a scholastic player?
Yes, but not using CT-ART...I'd recommend starting with either CTB or PCT before moving on to CTI (Chess Tactics for Intermediates) or CT-ART.
9) Do you use other chess training methods to supplement the circles?
While I was still training regularly, I was studying master games and doing some endgame study in addition to the tactics training. I also played regularly both live and online. I would then analyse and critique the majority of those games using Deep Fritz 10 and semi-regular input from the strongest player at our local club (he is currently a Strong Class A player and was USCF Expert rated about 10 years ago.)
10) Any general comments about chess training or the circles?
It can be hard work, but if you are willing to stay consistent and are determined to improve, this can be the ticket. I averaged at least 1-2 hours of study per day for close to a year and a half (not including playing time.) I'm somewhat the exception in that I did not find the circles to be drudgery, but truly enjoyed them. I think the work paid as I did see the "promised" improvement. I essentially improved 500 points across the board (online and off) in one year's time. Best of luck to anyone willing to take on the task of chess improvement!