Version 1.4 continues the quest that every developer of an emulator is looking for...better performance, smoother emulation, and improved compatibility with the huge library of games available for the ZX Spectrum. An ad-supported version is now also available for the first time, after a number of delays in getting the free version through the certification process.
As I wrote in the recent AAWP review, MetroSpec does the best it can within the environment of Windows Phone:
The proof of the pudding is in the playing, and it's very hard to come up with a definitive answer here, because much of your experience will come down to which games you decide to play. Many of the classic Spectrum titles that can be played in a rather deliberate way -- such as Jet Set Willy, Head over Heels, and Robocop -- will feel almost faultless on this emulator. Titles which need more keyboard interaction (such as The Lords of Midnight) and those that demand very fast and precise inputs (arcade based games like JetPac or Tornado Low Level) are going to be a little harder to play.