Thank you for the very kind comment. I really appreciate your words. I use the MP-E 65mm lens a lot more often lately for macro. It's capable of 5x magnification as opposed to around 1x one the 100mm f/2.8 (without extension tubes). I tend to shoot smaller subjects and shoot up close, and the MP-E setup I use with flash yields better results and has more versatility when shooting these small subjects. It's a specialized lens however, since you must be very close to the subject. The 100mm provides the range factor which is nice.
Typically I will pull the 100mm out if I want to shoot hand-held with natural light. It's great for larger critters like butterflies, dragonflies, bees, flowers, and even portraits. Both are great lenses, but since I've been fascinated with smaller subjects, the MP-E 65mm setup is usually attached to my camera. I thank many of the folks here for the help and inspiration. Great place to learn and nice reason to continue practicing.