The bookkeepers whose IT I've dealt with all use Quickbooks, and most of the small (and some not so small) businesses use Quickbooks too.
The only people I've ever heard say good things about Sage are accountants, or those who have never tried anything else (which usually applies to accountants too.) My own experiences dealing with Sage on other people's behalf have been uniformly bad - their expensive "support" would be laughable if there wasn't so much at stake, and their software is obtuse and can be picky about odd things like printers.
For myself, I use the open source GNUCash and have done for the past 7 years or so; it's far from perfect but for a small business generating tens of invoices per week it's fine; free, and possible to modify if necessary. Certainly vastly better than the version of Sage I paid for and started out using - I persevered for about a week with that before realising that I was wasting my time and had already wasted my money...