I use QuickBooks Pro for our software startup, and I like it. The nice thing about QB is that it is the most widely used financial software among small businesses, so any accountant you choose will be able to work with it. I don't know what country you are in, but I know they have a version for the US, one for the UK, one for Canada, and one for Australia.
The US QuickBooks Pro version can do everything you itemized in your question, except for maybe tax calculation. I know QB has a few tax reports to help during tax time, but I don't think there is one for estimated taxes based on expected revenues.
I'm not sure if you plan on doing your own taxes, or getting an accountant to do it. If you are doing your own taxes, one thing to keep in mind is that QB can integrate with TurboTax. All this means is that at the end of the year QB will create a file that you can import into TurboTax that will do most of the data entry for you. QB uses a proprietary format for this file, and TurboTax is the only tax software that will recognize that format. (TurboTax and QuickBooks are both made by Intuit).
You can still use other tax software to do your taxes, but you will have to manually enter the data. I used H&R Block's tax software last year, mostly because I don't like Intuit's business practices. If you have a decent understanding of the tax laws, it's not too bad, but it will still take you several hours to complete. If you don't have a lot of understanding of the tax laws, I would not recommend you do it on your own. Of course none of this matters if you plan to use an accountant.
There are other versions of QuickBooks. Some are more expensive than the Pro version, and some are cheaper. I think Pro is the right choice for most startups.
Note that our startup is a product based software startup, not a service based software startup.