Curently a unitary patent covers 17 EU member states: Austria, Belgium, Bulgaria, Denmark, Estonia, Finland, France, Germany, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Portugal, Slovenia, Sweden and Austria. 

Further countries will gradually be included; Ireland, Greece, Cyprus, Romania, Slovakia, the Czech Republic and Hungary.

Spain, Poland and Croatia are outside the unitary patent system, but a unitary patent can be supplemented by validations in these and all remaining EPC countries.

As the unitary patent is handled by one and the same court (UPC), legal certainty in the form of uniform law enforcement and predictability is promoted. As long as you want patent protection in more than a handful of countries, the fees incurred for a unitary patent will be lower compared to validating the European patent in these countries. It gets proportionally more cost-effective the more countries you want your patent to be valid in. For a limited number of countries, however, validation may turn out less expensive. In addition, you will run less risk of encountering a competitor who challenges the validity of your patent.

Requesting, obtaining and maintaining a unitary patent is easy. The request for unitary effect is filed with the EPO and the annual fees are paid directly to the EPO. The EPO also keeps a central unitary patent register, where you can check the validity of the patent, but also whether it, for example, has been pledged or licensed. If the patent is challenged, it will be easier to litigate before a single court than before a series of national courts. Hence, the cost of defending and maintaining the patent typically is lower. If you lose the right to a unitary patent, however, you will lose it in the entire region. Therefore, the rationalisation provided by the unitary system can, under certain circumstances, entail a greater risk compared to validated patents.

In most cases, the request will just be a formality, but in exceptional cases it can be rejected. If your request is rejected, it is still not too late to validate your patent instead.

Yes, that will be fine. The EPO keeps a central register of, among other things, licenses relating to unitary patents.

The court consists of a first instance and a Court of Appeal. The Court of Appeal is located in Luxembourg and central divisions of the Court of First Instance are located in Munich and Paris respectively. In addition, regional and local divisions of the Court of First Instance are distributed across several Member States. A regional Nordic-Baltic department is located in Stockholm, where the language of proceedings is English. If you wish your case to be tried by the UPC, a qualified representative is mandatory. Such a representative must be qualified to litigate before a national court in any member state or be a "European Patent Attorney" with the right to represent a party before the EPO.