As an accountant i use a number of different book keeping packages, and in the case of Quickbooks have been using it since version 5. As far as the 2010 version goes, adding back in multicurrency was a welcome change, and overall performance wise it's a bit quicker than the 2008 version as well. VAT has been changed somewhat again, with the main difference being that you can now file online through the program, although beyond that there arent that many changes.
As far as various versions and windows 7 goes, you can actually run anything from V.2005 onwards on windows 7 (either 32 bit or 64 bit) - although 2005 and 2006 do need to be patched before you start using it, although once this has been done i've found anything 05 and onwards very stable.
For someone looking at their first piece of book keeping software, it is still by far the most user friendly, simple, and flexible software out there, and while you could keep your figures on an excel spreadsheet, the main benefit with quickbooks is the flexible reporting, which allows a business owner to see exactly how he is doing at any given time. The other benefit, is that figures tend to be much better controlled through a proper book keeping package, which should save you in accounting fees as well (and given average chargeout rates, it might save you the cost in the first year).
The only proviso i would say however is that for new users not familiar with book keeping software, some help might be needed in getting started, as it can be a little daunting for someone looking at this for the first time.