I enjoy the ease of use the best. Over the years, QuickBooks has transformed itself from a steep learning curve to an intuitive interface. Even non-accountants can quickly get up to speed within QuickBooks Online. Many of the modules are excellent, particularly payroll, invoicing, time and expense, and financial statement report generation.
I dislike that the interface does not have checks and balances programmed in order to catch inconsistencies between modules. In order to catch these inconsistencies, one must perform manual, time-intensive reviews. Another dislike are the accounts receivable (AR) and accounts payable (AP) reconciliations. These two modules struggle because they require perfect customization and initial inputs in order to generate documents that surpass a certain accounting threshold.
If your Quickbooks Premier requirements are constantly changing then QuickBooks Online is an elegant solution. That said, I would not recommend that a low volume user switch due to the increased costs associated with the monthly subscription fees. Further, I am not aware of any upcoming features that QuickBooks is planning to roll out over the next year or two to warrant an upgrade for a low volume user.
The business problems solved by QuickBooks Online is the ability to automatically invoice and generate tax documents from the accounting records. It is excellent to be able to automatically generate 1099s and other documents, especially since these reporting demands are ever increasing.