I have the 3000X app bundle.
Serial decoding works brilliantly well, though it does have a limitation whereby it seems only able to decode serial data as it is captured, and doesn't work on stored data. So, you have to set up decoding correctly first, then capture data with the decoder enabled. You can't capture a data stream once and then play around reconfiguring the decoder options until it decodes correctly. Apart from that, which is a relatively minor inconvenience IMHO, it's great. (Note, bizarrely, the 2000X series can't do serial decoding on the digital channels - only the 3000X can do it).
The power measurement features look very comprehensive if you're in the business of designing circuits powered directly from the mains, but I don't have a current probe or isolated differential probe to use with them. Without this extra hardware, I don't think there's a great deal of benefit.