I'm absolutely sure they're woefully inaccurate. We've compared their data to our own GA data and their numbers are so far off it's laughable - or it would be if we weren't spending an arm and a leg to get them.

I have compared Compete's numbers to actual data from about 150 sites.

On that sample the numbers were never higher than actual and on average the Compete numbers were 2-3x lower than the actual numbers.

So I have used it as a reasonable estimate for half of the traffic a site sees. Although I may be placing my foot in my mouth because the stats for HN don't quite seem accurate: http://siteanalytics.compete.com/news.ycombinator.com/

Some of my sites receive 10 to 100 times more traffic than reported by compete.

Are they sites with less than 20,000 uniques per month? I've found those to be the outliers in my data set. They're wildly off on "low" traffic sites but have been a decent yardstick for sites getting more than 20k uniques in my limited experience.

No, more like 50,000-150,000 (depending on the month).

compete is a trainwreck. i wouldn't trust it, even for comparative analysis, at least based on the sites i've sampled

Would you mind expanding on this? Why do you think is a train wreck and where would you recommend to check for analytics?

Thanks!