The use of practical laboratories is a key in engineering education in order to provide our students with the resources needed to acquire practical skills. This is specially true in the case of distance education, where no physical interactions between lecturers and students take place, so virtual or remote laboratories must be used. UNED has developed a system to create and manage virtual remote laboratories, aimed at improving the way how practical exercises are conducted. This system is based on cloud computing and virtualization concepts. These "Virtual Remote Laboratories" (VRLabs) combine features of traditional virtual and remote laboratories but with clear differences over them, among others, VRLabs do not necessarily access real physical devices but are not based on simulations either. Each student is provided with a virtual remote laboratory based on virtualization that he/she will access through the Internet and will use to implement his/her practical assignments. We present details on how these laboratories are implemented for a subject in a post-degree program in our University. Furthermore, we also present an evaluation of the system used on such subject aiming at assessing the quality of the system regarding three different concepts, namely perceived usefulness, perceived ease of use, and perceived interaction. This evaluation is twofold, first, we have conducted a survey over the students of the subject, and second, we have performed another survey over the teaching team of the subject, both have been performed for the 2012-2013 and 2013-2014 academic years.