i did full install with all plugins i needed and it broke things in the site like other here say it does
you cannot register with comprofiler
links to their site all over the place
it would lower your SEO rating
This is simply not true. Of course there might be conflicts with other components, but if configured correctly, it will work just fine.
If you read documentation carefully, you should have no problems.
As regards links, I have already replied many times - if you mind them, get a paid version.