Peter. The dominant player in the start-up accounting software market is Quickbooks, and no one else is even close. They achieved this because, as the name implies, it is such a user friendly system. Accounting professionals used to scoff at Quickbooks as not being a very sophisticated system. Beign a CPA, I know; I was one of them. However, their growth has afforded them the ability to increase their products' features and abilities to be on par with many of the high end accounting systems. Now, most CPAS use it for their clients' books.
They now have an online version, which means the software and your data is stored remotely on their servers for a monthly fee, rather than incurring the expense and risk of it on your computer (or server). The online version also affords you the opportunity to quickly set up multiple users with various permission levels anywhere in the world as long as they can get an internet connection. It is CONTINUALLY updated with new features and improvements, rather than having to upgrade your software to the latest version. It works great, and I use it for all of my outsourced accounting clients. I pass along a big discount on the monthly Qb online subscription to all of my clients and charge a small monthly fee to process all of their transactional and reporting work for them. I'd be happy to answer any questions about it.