The number of mobile operators providing Internet access to end users is growing. However, irrespective of the access network, we observe a distinct sensitivity of user perception to response and download times, in particular for interactive services on the web. In order to facilitate the choice of the right network for a given task, this paper presents a systematic study of web download time and corresponding throughput as a function of the file size. Based on measurement data from three Swedish mobile operators and a particular strategy of choosing file sizes, we find surprisingly simple, yet sufficiently accurate approximations of download times. These approximations are based on simple-to-measure parameters and provide valuable quantitative insights into the acceleration of HTTP/TCP/IP-based data delivery. The paper discusses the emergence of these approximations and related errors. Furthermore, it correlates the findings with Quality of Experience, thus building bridges between performance, user perception and provisioning issues.