I am a US Chess Federation life member and A postal chess. I have owned a number of chess computers and chess software. As a USCF member I recently recieved, World Chess Live free for six months but I am really impressed. When my free runs out I plan to pay 4.99 a month. The featuresand flexability it offers are truly impressive. It offers chess news, a way to play opponents on line with all kinds of options of timelimits, type of opponents, odds, etc. It provides access to Grandmaster demonstrations and play, its own rating system, and a excellent chess computer software called dasher. Dasher has a ~ 10 computer "players" of various levels with own styles to play it allows you to choice time per move, color, board set up, computer analysis, etc.
The largest weakness are the standard weakness of computer software using brute force thinking. They suffer from lack of good king protection and strategic thinking beside material and center control, tendency to fall in repetition of position when ahead, and failure to see long enough ahead for Pawn promotion in endgame. The advantage this type of software is always see pieces hanging unlike human opponents.