As an appetiser, we watched Space Seed, the original series TV episode in which Khan (Montalban) first appeared. It's probably the first Trek episode I've seen in 20 years, and despite the wobbly scenery and dubious costumes (check out the compulsory mini-skirts for female crew members!), works simply because the characters are so well done. Khan, a survivor of the 1990's Eugenics Wars - still three decades ahead at the time - is rescued from cryonic suspension, only to hijack the Enterprise until Kirk goes to work with a convenient monkey-wrench.
Fast forward fifteen years, Trek time, and Khan is back, as power-hungry as ever (though the most evil thing is his disturbing resemblance to aging Lothario club owner, Peter Stringfellow), and desperate for revenge on Kirk, now an Admiral. Cue a battle of wits, rather than monkey-wrenches this time - indeed, the two foes never actually meet, only getting to curse each other through video-links, bringing it closer to Hunt for Red October than you might expect. This is especially so at the climax, where the two ships hunt each other in a nebula (shaped curiously like a plot device) that conveniently blocks their sensors.
The film combines the heart of the television show with big-budget production standards; the effects sequences have stood the test of time surprisingly well, perhaps because they are only used when necessary, rather than for eye-candy. The rapport between the leading cast members is excellent, and largely makes the movie - not a dry eye in the house for the final moments, either. While The Voyage Home may be the most enjoyable Trek film, this is among the best, and is quality SF by any standards, even for non-Trekkies like myself.