Thumbs Up Rated 4 out of 5 stars
The add-on has a number of benefits for any one within SEO, but must keep a keen eye on not relying on it too much.
Yes, it injects its ad into the SERPs (an annoyance imo), but the benefit I get for quickly seeing nofollows, PR, indices, etc. outweigh a minor annoyance that I can just click off when I do not need to use it.
As previously stated, be careful on setting the "onload" ability as you will likely get blocked from Google and evidently Google does not like you even often checking the cache dates as well.
Avoid those areas and the program will work well with the plugins.