Samsung's $2,899 Galaxy Z TriFold works well as a smartphone, especially for entertainment, but falls short as a tablet and laptop, marred by unpredictability (Chris Welch/Bloomberg)

Chris Welch / Bloomberg: Samsung's $2,899 Galaxy Z TriFold works well as a smartphone, especially for entertainment, but falls short as a tablet and laptop, marred by unpredictability   —  The company's experimental new phone can fill in for larger-screen devices, but isn't close to replacing them.