I suppose it depends on your level of sales but I have always employed an accountant and a book keeper,I would never do it myself.
Yes its worth it correct accounting saves a whole lot of hassle from the tax man , the last thing I want to be doing when building my business is to have to set aside a chunk of time to do my books.Also a good accountant will also be able to offer valuable advice on tax savings.
As I said we also have a book keeper who does the daily stuff and keeps on top of the financials for when the accountant does your end of year, this can save you a lot in accountancy fees. A book keeper can also do your invoice chasing four. You need a book keeper when starting out for no more than a few hours a fortnight/month, our book keeper comes in once a week for 4-5 hours and we pay her hourly.