I honestly can't understand the reception this film has gotten. I thought Bullet to Beijing was an excellent film, one I thoroughly enjoyed. Okay, so it's not as good as The Ipcress File, but did you expect it to be?
People often complain that Palmer has lost much of his wit from the 60s, and I give the film-makers credit that they didn't try and imitate it. Palmer is now getting on, even before he loses his job at the beginning, he is clearly close to retirement anyway. What wit he does come up with is funny in its own sense - watch for the comment about the milk for instance. Caine is his usual superb self, and there are good performances all round. I would put Jason Connery's apparent 'woodeness' down to the fact that he plays a very serious and solemn character. As he opens up more and more, he becomes less 'wooden'.
The film is extremely fast-paced, and not just because it's on a train - all the crosses and double-crosses happen in the context of racing towards a deadly conclusion, whereas The Ipcress File for instance, often stood still until Palmer discovered something new.
Excluding Billion Dollar Brain (which I haven't seen) I would say this is the second best in the Harry Palmer series. Certainly it is much better than the awful Funeral in Berlin, and the sequel to this, Midnight in St. Petersburg, didn't offer the same level of excitement.
You might have to watch it more than once to fully understand it, if you're not concentrating. But is that something to complain about?
Incidentally, Jason Connery's non-Russian accent is explained within the film.