I don't know about you, but my servers have better things to do. Though WebTrends is very fast, and its integral HTML reports are great, speed and reporting alone aren't enough. The ability to export data and to keep it in a standard, accessible database format are essential. Because it lacks these features, WebTrends is a second-tier program, though you can't beat the price. Not only is Bolero a great piece of music, it's a great Web-hit analysis program.
Bolero has many virtues.
Chief among them is that it can work in real time with multiple servers. That will increase your internal network traffic, but I'd pay the toll of a bit more network congestion for composite data from all my Web servers any day of the week. Besides, you can set Bolero so that your Web server actually speeds up. Bolero manages this stunt by intercepting logging information on the site and taking care of logging data and domain names. If you choose to use this option, you can switch off these services on the Web server so it can spend more CPU cycles doing its primary job.