Thanks for the detailed feedback.
1) As far as missing symbols go - we are constantly working on adding new symbols to our database and we actually have a board
on this forum where users can request new symbols to be created. Please feel free to add your requests for the ambulance and hospital etc
2) I am aware of several broken symbols in the library (there were some problems with the conversion to SVG from the original Illustrator files) - I am going to try to get all these fixed in the next couple of weeks.
4) While I agree that things are not completely smooth as yet, I do think computer speed and browser improvements will help this. However, you really can't compare this software to Paint. Have you ever used Inkscape, Illustrator, CoreDraw or some other vector package? They all require a decent learning curve and by nature are much more complex to work with, an not necessarily intuitive to a novice vector user. However, the advantages to vector graphics are many. If you'd like some more info on this, let me know.
5) Regarding saving issues - the way the browser saves the file is not something we can control. We are thinking of giving users the option to save their diagram to our servers so we can better manage versions etc. As for the "because it was likely to cause harm" message - I am curious to know what browser and version you are using and also what anti-virus software you are running. I have not seen any messages like this. Regardless, what you are saving is either an svg or png file, which really has no potential to cause any computer harm
6) I am very sorry to hear about your hdd crash, but I really can't see any possible way the diagrammer could have contributed to this - perhaps the fact that your computer was that close to a hdd failure may have been partly to blame for some of the issues in using the diagrammer. As for it being only 5 month old - hdd crashes really can occur at any time in the life of a drive. I hope you get it sorted out quickly and haven't lost too much data. Keep in mind that often drives can be recovered (sometimes with free/cheap software) or at substantial cost, even if they can't be booted from.