A few weeks ago, I returned to Trillian after many years away. During Trillian's absence from my computer, I initially ran nothing at all, and then tried out Digsby for a while. A long-time Trillian Basic user (before the existence of Trillian Astra), I switched back to Trillian due to having recently purchased an Android phone; Trillian's cloud history was the primary incentive.
Today, I finally got around to uninstalling it. Unfortunately, in the current form, the ads that Trillian displays are far too intrusive for me. The worst were the ones that popped-up as notification windows that needed to be clicked away (they don't disappear after a time period), but the ones inserted into the chat windows were annoying as well.
It's a shame, really - the rest of the program is superb, and if you're up for purchasing the ad-free pro version, don't hesitate to do so. However, with excellent free alternatives such as Digsby (watch out what you allow to be installed along with it, though) or Pigdin, I had very little patience for the intrusive ads shown by Trillian. If they ever change the way ads are shown, I'll be back; the conversation sync with the Android client is too good to pass up, but it didn't outweigh those darn ads.