I don't have the S90, but do have the Ricoh GRD3 which uses the same sensor. On a recent trip to Haiti, I used the GRD3 in addition to my R-D1, while a photographer I was with used his GF-1 in addition to his Canon DSLR. Both of us used the smaller cameras more than the larger ones. Both of us were also happy with purchasing decision we had made in deciding between the GF1 and GRD3. For me the things I appreciated with the GRD3 was the 28mm equivalent view, the depth of field, its size and its silence. I was happy I brought the Epson too, because I did like to take some shots with a shallow depth of field, and sometimes the 28mm was too wide. Being a zoom, the S90 would take care of the latter, but given the small sensor, not the former.
In May I will be showing some of the prints I have made of shots from that trip during CONTACT, Toronto's photography month. They will be a mixture of shots made with the Epson and with the Ricoh. The prints will not be exceptionally large, at most 10 x15 (I don't usually print bigger anyway.) I suspect the only people who will be interested in which pictures were taken with which camera will be my flckrite friends and RFFers who I hope will come to the show. If this means I'm not serious about photography, so be it.