Been Limited for a few years now,
The only downside is the additional accountants fees as they need to supply a set of audited accounts for submission to Companies House each year, our accountants fee is £395 for the year against £195 for sole trader accounts.
On the plus side, you pay less tax as you take a basic wage (£7,200pa) and then a company dividend which incurs 20% tax as opposed to drawings which incur 23% tax. Plus if it all goes tits up, your house and savings are safe.
I would disagree with Rogers comment though, you do need to declare your limited status on all paperwork as this may affect a clients perception of you and how they treat your credit rating, you cannot hide behind ltd status if it is not on your paperwork.
I have just taken an individual sole trader to court when they defaulted on a payment, none of their paperwork said they were ltd, but they were and they tried to hide behind it. The court ruled in my favour as they had not been open about their ltd status, she now has a CCJ against her as an individual..... so her credit rating is now basically f..ked!!