Royal Mail - SmartStamp

I have been looking into the best way of sending mail without having to go out and buy stamps every day, i have found these options so far:
- Stamp books of 100+ or rolls of more.
- Buy a franking machine
- Use SmartStamp

I have heard that for companies that don't send a massive amount of mail, franking machines are a bit of a waste of money considering the charges, then i found out about SmartStamp - has anyone ever used this service? It looks like it might work quite well, but does anyone have any experience with it?

Also, what methods do you use to send mail?