It depends on what results you want to achieve?
If Open Office does everything that you require it to do, then I don’t recommend changing, but I would advise you to sit down and think about your accounts from a long term point of view.
I started off years ago with a simple spreadsheet - 3 tabs, Quotes, invoices and Purchas orders. Then mail merged into word. Sounds similar to what you have currently set up. In the beginning it was perfect as the business was new and I did not get a lot of transactions and I only had one division of the business.
But the business grew over time in number of transactions, I diversified my work etc.
I found huge limitations with the excel spreadsheet/mail merge as time went on. For example, I had to trawl through the spreadsheet to find the part code of a laptop that I bought for a client, so that I could quote for a new client. Manager has an inventory option which allows me to quickly find the part code. Secondly, I had to copy info from that spreadsheet to another spreadsheet to see what my VAT bill was going to be. Manager allows me to see real time what my eventual VAT tax bill is going to be as I process each transaction. Manager allows me to see immediately how much money is coming in from sales, how much money is going out for purchases and this allows me to keep track of cash flow.
Manager allows me to see how much profit I make from sales of goods, how much from IT Support, how much from website services, how much from network cabling installation services. I could never do that with the Excel Spreadsheet.
In short, don’t think of Manager as a program to just record your invoices and expenses. If that is all you want to do then your excel spreadsheet open office solution is more than sufficient. But if you want to know which customer is your most profitable, if you want to know what you make the most/least money from and so many other questions like this, you cannot do this (easily) with spreadsheets and open office.
Manager is run by one developer, which means that he has limited time at his disposal, so things like documentation sometimes get left behind. I agree that the guides are a bit too brief, but he has only just started to update the guides in the last couple of weeks. What I like about Manager is that he fixes problems far quicker than any other company I have ever dealt with, he is interested in listening to feedback so will add new features if he feels that enough people will benefit from the feature and the best feature is that the program is so simple to use.
On the Partners page there is a link to a youtube channel giving you a bit more of an overview of Manager and there is also a company that can design your sales invoice template for you.
Of all the accounting programs that I reviewed three months ago, I chose Manager because its so easy to use and I like the layout and GUI concept of the program. Its also a very small program as well.
Spreadsheets are perfect if you just want to record invoices and expenses just to bill the clients, but if you want to get information out of the spreadsheet such as what services make you the most money or client that is the most profitable or real time cash flow information or anything like that, spreadsheets are just not up to the job. I learnt this the hard way as I started off with spreadsheets which were adequate at the time but as the business grew became hopelessly unsatisfactory.
Hope this info helps.