They also have a huge set of T&Cs you have to agree to. I'm quite anal about carefully reading any small-print, so this added more time onto what should have been a very simple transaction. There's some complete nonsense in there too - the best bit was: "You cannot purchase Postage Labels unless the computer from which you are using Online Postage is connected to the Internet." Well, DUH! Just after that there's a very short list of supported operating systems and web browsers (under these T&Cs, my parents wouldn't be allowed to use the service via their Win98 PC).
Another particularly daft part of the site was where it asks you how heavy the packet you want to buy postage for is and points you at a page that tells you how to estimate the weight if you don't have any weigh-scales, then says immediately afterwards not to estimate the weight of a packet you want to buy a postage label for. Why mention estimating the weight at all if they don't want you to do it?
The final annoyance was that it only lets you buy one label at a time. Since I wanted to send two identical packets, it would have saved me a fair bit of time if it'd let me enter two addresses and print them both on one sheet, and presumably would have saved RM some money in per-transaction credit card fees too.
Having said all that, I like the way that it generates a printable address label for you, and it's good that they don't have a minimum order limit. If they could make the site run faster I might stop using stamps altogether.