The promise of Mobility-as-a-Service (MaaS) is that it decreases the need to own a car and contributes to a more sustainable transport system. However, MaaS also offers relatively easy access to car-based travel alternatives which may result in substituting public transport trips by car trips. An important question therefore is: Which type of traveler is going to adopt MaaS and which impact is this going to have on their mode choices? This paper explores this question by presenting the results of a stated choice experiment conducted in the Netherlands. Travelers are presented with MaaS bundles that vary in accessibility to transport services and price and they respond to a range of questions about bundle adoption, change in transport mode, and willingness to shed one or more cars. The results suggest that if MaaS bundles are given for free to the travelers, this has the potential to change their frequency of mode use. For example, if the MaaS bundel includes unlimited bus, tram and metro (BTM), even travelers who solely use car will then use BTM more. However, realizing this potential is not very likely, because when travelers have to pay for MaaS, adoption rates are rather low, in particular of those who use car the most. In addition, the willingness of car owners to shed their cars is very low, suggesting that currently MaaS is not conceived as a viable alternative for car-ownership. On the other hand, current public travelers seem most interested in MaaS and results indeed as expected suggest that this increases their car use. Overall, the trends reported in this paper adds to a growing insight that MaaS' contribution to sustainability may be smaller than generally believed.