The new site, Ohdontforget, will send a text message to a cell phone at the time and date you specify. If you set the send time to "now," you can use it to send regular SMS messages, as well.
Is the service missing important features? Yes, tons of them. No Outlook sync, no log of messages sent, no address book, and if you're sending an SMS to your wife, for example, she can't see who sent it (the return address is ohdontforget). And there's no way the site makes money, as far as I can tell.
But simplicity is beautiful, and by that metric this site is a knockout.