The first thing I would like to say is that Zabbix team did a great job and I really like Zabbix monitoring system. But there was one annoying thing that often confused me and my teammates. In opposition to some other monitoring systems (cacti, for example) generated graphs are too sharp and values gradations was not like the real deed. You can look at an example in attachments. More often gathering values - more peaks we see. So I've decided to make graphs more smooth and in the second picture from attachment you can see what I got. Graphs looks more smooth and more likely.
Before applying patch you should alter your DB shema. You need to add field "smoothness" with type NUMERIC(1,0) for table graphs_items. After applying patch you should be able to set smoothness parameter for graphs items. 0 - smoothness off, 1-9 - sets smoothness level.