I am very happy with Delta's on-line statements. They are timely, usually correct, at least for the flights. I also like diff breakdowns - segments YTD, miles this months, etc. Also shows my old FF mileage.
However, the statement which just arrived lists the flights I took in June, which frankly I have already forgotten about, especially the bonuses/promotions/etc. available at a time. That's my only beef w/Delta, albeit a small one. Don't know much about other airlines' sites, I am a DL only.
Hilton's new site is improved. However, their paper statements seem to arrive randomly, 2-3 mos after the quarter end. I am using the on-line info now.