Time reversal, that is prefiltering of transmitted signals with time reversed channel impulse responses, may be used in single user communications in order to move complexity from the receiver to the transmitter, and in multiuser communications to also modify statistical properties of multiuser interference. Imperfect channel estimation may, however, affect pre- vs. post- filtering schemes in a different way. This issue is the object of this paper; Robustness of time reversal vs. All-Rake (AR) transceivers, in multiple access communications, with respect to channel estimation errors, is investigated. Results of performance analyses in terms of symbol error probability and spectral efficiency when the receiver is structured either by a bank of matched filters or by 1Rake, followed by independent decoders, indicate that AR is slightly more robust than time reversal but requires in practice more complex channel estimation procedures since all channels must be simultaneously inferred in the multiuser communication setting.