First off, let's get a few things out of the way:
Yes, "Brainstorm" is marred by uneven acting and the death of its lead actress, Natalie Wood, under circumstances that to this day are still the stuff of speculation.
Yes, Louise Fletcher's death scene is overacted to the point of parody.
Yes, it's not easy to accept Christoper Walken in a role of a semi-normal person.
Yes, "Brainstorm" was only Douglas Trumbull's second film as a director, and some might argue that it was little better than "Silent Running."
But, even despite all of that, the story is incredibly engaging, the visuals are striking (what else would you expect from the wizard responsible for "2001" and "Blade Runner"?), James Horner's music is absolutely divine, and the film is quite enjoyable.
Also, in its favor, a great deal of the credit (or blame, as many would say) for the final result lies squarely with MGM/UA. Still dealing with United Artists' financial baggage after their merger, the company all but took the film away from Trumbull after Wood's death--not to mention the studio's lack of support for Trumbull's plan to film the "helmet" sequences in his ultra-realistic Showscan process.
So, in point, I highly recommend this movie, but just be aware of what you're getting into...