The HIARCS engine uses the Fritz 12 GUI which I happen to like a lot. As for the engine itself, HIARCS is best known for its unique human-like playing. Chess computers don’t really play like humans, they play like computers. However, many players think HIARCS’s play is the most ‘human-like.’ It's not overly-aggressive and it doesn’t seem to play what can only be described as weird moves.
Like all engines, it is good at tactics but is best at positional play; but probably not as good positionally as Shredder and Houdini. This makes HIARCS a good training partner for the reason that it does play human-like moves and on the handicap levels it makes human-like mistakes. For this reason, it may not be best if you are looking for absolute best move.
Hiarcs ranks way down on CCLR’s Complete List with a rating of 2997 which is still pretty good. By comparison #1 ranked Houdini 4 is 3248 while Stockfish DD is #3 at 3229 and Houdini 1.5a is #9.
One disadvantage is that HIARCS 13 offers single core engines Hiarcs 13.2 and 13.1 but if you are using it as a sparring partner rather than looking for the best move, this isn't an issue. It has the Hiarcs13Lite opening book, Fritz 12 interface with many training functions, a database with 1.5 million games and 12 months access to Playchess.com.
Opinion: if you are looking for a realistic training partner, HIARCS is worth considering if you don't mind the rather steep price just for a playing partner.