These two episodes are quite neat: admittedly, they might be a little slow, but the pace always feels measured, rather than dragging. There's also the development of a theme: the crew (and by extension, the Doctor and company) are frightened of their fellow mineralogist John, and then again of the Sensorites, and in both cases it seems like this is largely because none of them have tried to talk to them; it takes Barbara and Susan talking to John to realize that he shouldn't be feared, and while the Sensorites still seem to pose a threat, Susan's act of communicating with them appears to reduce the tension somewhat.
The Sensorites themselves are (feet aside) rather wonderful designs. It's really an excellent headpiece, looking alien yet not too abstract. They're not the most threatening-looking creatures, but then the script drops hints that they're not supposed to be: "I think that they were as frightened of me as I was of them," Ian comments after holding them at bay with some sort of tool. Indeed, one gets the impression that the Sensorites have been forced into menacing the crew and preventing them from leaving, and that it's not their preferred state of affairs ("Once before we trusted Earthmen, to our cost," comments one Sensorite) -- indeed, it would seem that the Sensorites are the unwilling warriors of the episode's title, rather than the crewmembers (as one might have surmised at the episode's outset). There are also some nice educational touches, such as the discussion of a spectrograph, melting points for iron and molybdenum, and the bit about the contracting of the iris (as far as the Sensorites go, evolutionarily silly, as has been pointed out before, but not inaccurate based on what we're told). And special note has to go to the direction of the beginning of "Strangers in Space", as the camera follows the TARDIS crew straight out of the console room and into the spaceship -- and then we cut to the side and see the police box, seemingly standing where the other camera just was. It's a neat little bit of direction, and slightly surprising to see so early -- they're still trying to do things like this on Doctor Who now, and Mervyn Pinfield was doing it in 1964!
In fact, in many ways this feels a lot closer to the style of Doctor Who as we know it than anything that's come before it. The Doctor's taken a leadership role, asking the right questions and showing Maitland and Carol that they can resist the Sensorites' control, while Barbara and Susan go off exploring the ship and, while they're threatened initially by John, they become proactive with John and befriend him, rather than needing to be rescued. As much as people may not want to admit it, it's not too far of a stretch to see this as, say, a Matt Smith story -- the Doctor discovering that they needn't be as afraid of the Sensorites as they have been could just as easily be something that the eleventh Doctor would do as much as the first. Before it's seemed as if this show could do just about anything. That's admittedly still the case here, as the production team are just trying out a different style of script here -- there's nothing to say that this will set the tone for the show in the future, but with hindsight we can see the Doctor Who we know starting to really take shape.