The performance of functional items, such as headphones, cameras, etc., can be simulated in the context of a network-accessible electronic catalog by using virtual machines, and similar techniques. An electronic marketplace may provide a user with the option to sample the performance of an item being browsed, and can generate and/or configure one or more virtual machines to simulate functions of the item, using parameters that are specific to the item and/or that are tailored to the user's device. In some cases, the performance of different items can be compared, e.g. by simultaneous presentation of visual information, and/or item(s) performance can be virtualized in various ways that allow the user to identify differences or capabilities that might otherwise be difficult to discern. The described methods may also recommend products that closely match the user's preferences based on the user's modifications to virtualizations.