Roland,
Here are my best answers to your questions:
1. The auto straighten is a function of my ScanSnap S1500M. I also have a MFP with a flatbed and feeder. That does not have the auto straighten function. S1500M will auto rotate if you insert the pages upside down... or even if every other page is upside down, etc. It will also remove blank pages, scan full duplex, auto-crop, etc. It does it all at blazing speed.
2. I have never used the AI features before (such as auto classify), but your post prompted me to try it. It is really quite amazing. I just scanned my corporate Amex bill. I selected it in the inbox, and opened the Classify sidebar. It showed me a sorted list of "matches" by relevance, with my corporate Amex folder at the very top and pre-selected. Below that was a list of "next best" matches. The second best match was my personal (vs corporate) AMEX bill. This one, as well as the matches further down had much shorter relevance bars. I simply left the default (correct) cloice highlighted, and hit the "move to" button and it was filed away. Thanks for forcing me to look up this function!
3. I also have a bunch of Costco receipts scanned, and confirmed that my "reverse image" totals do NOT OCR match. Honestly, I am not sure that I really care. I just did a bunch of random searches such as "costco television", "costco hp", "costco Nikon" and every one of them instantly listed the correct receipt at the top of the search window with the longest relevance bar.
You can annotate the receipt using the DTPO editor, but I never do that. Search is so easy that I do not spend a lot of time trying to over classify things. Maybe my needs are just modest.
I hope that helps.
/Jim