Don't worry, I don't get offended and I don't mind to offend others. If someone gets offended because of what someone says they have issues. There really isn't anything to troubleshoot. I'll go along with luck and variance on most cases. I can confirm my little miner running smoothly at home, hasn't budged from 560Gh/s for many weeks now according to CGminer. Where it does change is at the guild pool. CGminer says 560Gh/s and the guild says today 580Gh/s. I did read a post about how/why that happens, just have to go back and look for it. It was well spelled out. Time for some overclocking a little.
Pools estimate speed based on share submission rates. Just like the pool has variance in solving blocks, your miner has variance in solving shares. While the two numbers should be fairly close, you will generally see 5-10% swings up or down on the pool dashboard. If you look at the Charts page, you can see these fluctuations in your estimated speed based on share submissions. You'll notice the 1-week chart is a much steadier line, since this uses 4-hour averages instead of 1-hour averages.