I have the paid version...I tested sending a scheduled delivery to my other handset a Z10 the sms was received immidiately. I scheduled it to be sent in 5 minutes. Does anybody here has the same thing happening?
This was a reported issue, but I believe it was fixed in the last release. You can try the beta (add http://cydia.bitesms.com to Cydia's sources) and see if it helps at all. If not, you should let the developers know. They're very good at fixing issues quickly.