Yeah its a safe and enough good tool. I check keyword ranking using SEO quake.

No problem, just don't get all click happy trying to search Google too fast or they'll do a temporary block on your IP. Even If they block your IP, all you have to do is clear your browser (CCleaner) & reset your modem which only takes a couple of min. (faster than waiting on the blocked IP to clear).

I use chrome seo quake for this is the best tool for website optimization and evaluation.

SEOquake is the primary toolbar that all webmaster try at first hand. However, at times it makes Firefox slow down. Even so, I favor it since you can turn off the toolbar with just a click and can be set it up in many ways you want.

SEO Toolbar by Moz and SEOBook SEO toolbar are other favorite ones that I found very useful for SEO purposes.

I refer you to use SEO quake in google chrome if you don't have google chrome then you can also use firefox.