Until I read the feedback from my post I had not paid much attention to the specifications for the various cards. As a result of reading the posts and doing a little more observing I have noted that the "speed" ratings (400x; 600x; 800x, etc.) are not consistent with the "read" ratings of the cards (45MB/s, etc.). For example, the read speed for the Lexar 800x card is 45MB/s and the speed rating of the Sandisk 90MB/s cards ("Extreme Pro") cards is 600x. So do the "speed ratings" (400x; 600x; 800x, etc.) mean anything? It appears from your experience that the read speeds are what one should consider, not the "speed ratings". That is helpful information. I had assumed that the speed ratings were indicative of the speed of the card. I therefore had planned to buy the Lexar 800x card if I did not buy the Lexar 1000x card. It appears that the choice really should be between the Lexar 1000x card and the Sandisk 600x/90MB/s/Extreme Pro cards. The information you provided is what I had hoped to obtain with my post. Thanks for sharing your experience.
If anyone can provide any information with regard to the apparent inconsistency of the "speed ratings" vs. the read speeds please do so. I find this very confusing and inconsistent...but I don't purport to understand any of it beyong reading the numbers.