I would have to disagree with FF..

I have been a Diners card holder for the last 5 years... and I have had no problems whatsoever..

Since I travel a lot the advantage of the Diners card is as follows:

1) No preset speninding limit
2) Excellent travel insurance (much better than CIBC - which I used to own)
3) Accepted vitually at all hotels and airlines and at more retailers as well... I went to the Keg for dinner the other day, and they accept it !! More stores are signing up for the Enroute...
4) ** My favorite*** 60 days till payment... It certainly came in handy since I tend to be quite late in submitting my expense form... There is NO penalty or interest if you pay within 60 days.
5) If you do a lot of international travel (esp to Europe), the lounges are wonderful and could rivals that of many airliners.

Btw... the regular silver card is only $65/year annual fee NOT $120.