A fun, tense episode that's fast paced enough (especially by the standards of the era) enough for it to skip quickly past the oddities (pumping up the adrenalin in an old man wouldn't make him super strong and impervious to phasers, it'd probably give him a heart attack). There's a hell of a lot of stuff going on in this one compared to the rest of the season and most of it is very strong.
But of course, it's the exploding head we all remember. Still strong enough to be cut out of the most recent SyFi screening of the episode in the UK (I wonder if they'll do what the Beeb did and leave it in Shades of Grey
?) it's a brilliantly insane OTT bit of violence.
It's actually amazing Gene let that one through considering his general attitude towards the unblemished purity of our heroes at the time; Picard and Riker don't have any real reason to shoot Remmey. He's unarmed and they don't know killing him will switch off the plot. Without that knowledge having him alive gives them a hostage. Having him dead could have just really, really, really pissed off all the infected officers at Star Fleet headquarters... Such an arresting visual though I'm glad they did it.
I also love that when Riker calls for security Worf (and for some reason Geordi, obviously he had itchy feet at this point but hadn't decided on his new career path) turn up unarmed, but Crusher arrives packing a phaser.