I don't think this could be classed as spoilers, I was going to use a spoiler tag but I have no idea how. If this could be considered spoilers please tell me.
For me I thought it was a good anime but FAR too short. The SAO story arc was just too short for an SAO anime, it should've been an entire season maybe more just for SAO. The AO arc shouldn't have started so soon, I feel they should have shown the characters adjusting to normal life for a little longer for character developments sake. All in all it was good but too short for it's own good, but if it had to be only 25 episodes I'd say they did pretty good under the circumstances.