> When I updated my Emacs from master a few days ago I noticed that
 package installation has been changed significantly:
>
> * the process starts with the super cryptic message "Transaction started"
> * the process ends with the super cryptic message "Transaction done"

What do you think could make them less cryptic? I'd rather not spam the
echo area with progress reports.

> * you get no visual indication that something is being done

Yes, something should at least be added to the mode line process.

> * package compilation warnings are now to visible

That's intentional. The warnings buffer is still created, but I think it's
bad user experience to pop up a bunch of warnings that are not the user's
fault.