Virtual and Augmented Reality are developing rapidly: there is a multitude of environments and experiments in several laboratories using from simple HMD (Head-Mounted Display) visualization to more complex and expensive 6-wall projection CAVEs, and other systems. Still, there is not yet a clear emerging technology in this area, nor commercial applications based on such a technology are used in large scale. In addition to the fact that this is a relatively recent technology, there is little work to validate the utility and usability of Virtual and Augmented Reality environments when compared with the traditional desktop set-up. However, usability evaluation is crucial in order to design better systems that respond to the users’ needs, as well as for identifying applications that might really gain from the use of such technologies. This paper presents a preliminary usability evaluation of a low-cost Virtual and Augmented Reality environment under development at the University of Aveiro, Portugal. The objective is to assess the difference between a traditional desktop set-up and a Virtual/Augmented Reality system based on a stereo HMD. Two different studies were performed: the first one was qualitative and some feedback was obtained from domain experts who used an Augmented Reality set-up as well as a desktop in different data visualization scenarios. The second study consisted in a controlled experiment meant to compare users’ performances in a gaming scenario in a Virtual Reality environment and a desktop. The overall conclusion is that these technologies still have to overcome some hardware problems. However, for short periods of time and specific applications, Virtual and Augmented Reality seems to be a valid alternative since HMD interaction is intuitive and natural.