I have a full version of Poweramp and very happy with it. I however have experienced some problems with last.fm scrobbling from this app. I am using Simple Last.fm Scrobbler, and I am aware that it is difficult to know whether this is a Scrobbler or Poweramp issue, but one has to start somewhere.
The problem is that not all tracks scrobble. Sometimes one or two tracks from an album will just randomly not scrobble. Both last.fm Scrobbler app and the Last.fm webpage show these tracks as "now playing". There is nothing that makes these tracks different than others which scrobble successfully.
This was a problem a month or two ago, then it disappeared, and it came back again just one or two days ago.
Scrobbling from other sources besides my Android phone work fine.