> If I convert dollars to bitcoins, I would be tempted to wait a couple of days and sell on mtgox and then buy the service with dollars.

Remove the "purchasing a service" element out of the equation and this still holds up -- the temptation to put money aside in bitcoins is still there.

As the service is a month-to-month thing, there's a limit on the amount of time you can wait if you did purchase by bitcoins. Also, if the price of bitcoins is going up, it's encouraging customers to pay earlier and earlier which is a good thing as most customers seem to wait until the last day (but server bills come up before then...).