The ease of use, ability to see all logs in one place without having multiple programs open at once! I wish there was an app that would sync with our server for automatic log rotation so we wouldn't have many files sitting around unused (I do like how it auto rotates as well).
Definitely check out their trial version since you get about 30 days or 1 month free when signing up - this is what got me hooked into using them forever!! It's very easy to setup alerts/notifications etc via email notifications which lets us know immediately if something goes wrong within minutes after first signup rather than hours later. We are able save time by not searching through emails looking for errors from months ago but instead just let someone else deal wth old ones while also being alerted instantly upon new issues happening now. Also helps keep track of everything going down internally during dayto date operations vs older stuff lying dormant until.