Thanks for considering giving users a choice. The old interface's in-your-face Note field was essential for me - I enter a note for every transaction, allocating it either to me, my husband, or the both of us. This enables me to reconcile our finances at the end of the month.
With the old UI, I was able to immediately see which transactions required allocation, and I could quickly do so by tabbing through the fields at the same time as I was picking categories. The new UI forces me to take my hands off the keyboard and click on the Details tab, then the Note field, enter the note, and click Save.
On a side note, I discovered a bug: pressing "(" while entering a note in the Details panel will close the panel. Reopening the panel shows your note text is still there, but no note icon appears on the transaction list and your note will NOT be saved.
I have a solution! If you use Firefox (and possibly Opera), I have written a Greasemonkey script which brings back the Notes column's text display. It's not perfect, but it lets you see a note summary for all your transactions, as it was in the previous release of Quicken Online.
This is a work in progress; the note display is only generated when the page first loads. After any sorting, editing, etc. the summary disappears. Just refresh the page to redisplay note summaries.