Lack of support for Cyrillic e-mail addresses. At the moment, you can not create e-mail the form админ@мойсайт.рф, the name have to be in Latin, ie admin@мойсайт.рф. But, unfortunately, it does not save you from the problems at work, many mail servers do not support this kind of mailboxes.
Additional difficulties in the CMS on this domain. Not all content management system correctly understand the Cyrillic alphabet and when setting instead of the site have the chance to see strange symbols.
You lose customers from abroad, as they do not have Cyrillic characters on the keyboard. And the address of your site for them will look very strange because of problems with the encoding.
It is very difficult, and in some cases even impossible to add to your site RSS-feed or configure authorization for the account of one of the social networks. The absence of such simple things on your site can scare off potential customers and reduce the overall attendance.
And the biggest problem associated with the promotion of the site. The fact that not all perceive sayty2 links like yandeks.rf for them they are converted into punycode and will look like this: xn--d1acpjx3f.xn--p1ai. To put it mildly, not very readable and beautiful, hardly anyone would want to share with you this link. And in the registration of such links in a directory search engines have to recode them back into a readable form. Because of what the “weight” of such links may significantly decrease.
To summarize. Most experts believe that the best solution to date is to use the domain in the zone .rf as a “mirror” or redirect to the primary site, which is more familiar domain zone. It really is the most reasonable solution at the moment, because to ignore this area and to give up new opportunities meaningless. Not long ago, the Russian language has become the second most popular on the Internet.