The New York Times has a piece on visa services. I contribute,

Gary Leff, a co-founder of Milepoint.com, a website for veteran and would-be frequent fliers, and the blogger behind the miles and points site View From the Wing, has directed his readers to Allied Passport and Visa, which has given them discounts. He said the feedback from readers who have used the visa service has always been positive, though he has yet to try it himself because he’s one of those frequent fliers who have not been able to part with their passport.

I never used them because I lived in DC where countries all have embassies. Now that I’m only in DC about a week a month I will use them. For the record I’ve not taken any special consideration from them, I only use the best available public offer, but all the feedback from readers who have used them has been enormously positive.

I think it’s useful to,

• Always check whether or not you need a visa when you book tickets and potentially even again before you travel. These things do change. Egypt has new requirements. Turkey recently eliminated visa on arrival. Venezuela instituted new rules.
  
• Develop a relationship with a visa processing company who can offer you advice. For instance, India has new rules that allow online processing and approval for tourist entry, but what if you will enter and then leave and come back through India on your return? Turns out the process doesn’t allow re-entry for a defined period of time.

These things are complicated. Although for the self-service inclined a great resource is the TIMATIC database accessible via the Star Alliance website. I always look up visa requirements myself, and it’s useful to see just what the airlines will see when they look up rules for your travel.

Brazil was a pain when I did that one a couple of years back, if only because not only do you have to go and get money orders (which is common) but you also have to send things via USPS Priority Mail (and not FedEx and similar). Who uses Priority Mail any more?

And the last time I did India they wanted me to list every country I had visited when there was only space on their online form to list about 5. I included an addendum with my package, although the truth is they probably just wanted to know if I had been to Pakistan.

A visa company can make things easier largely because they know the process and do it frequently, so they know what instructions actually mean (usually) and what to expect in response from an embassy or an outsourcing company used by the embassy. Often instructions can be confusing, people get things wrong, so having someone walk you through the process can help – and the fees are frequently quite modest (the biggest fees will be charged by the country whose visa you want, plus for all of the document shipping).