Just re-watched it...
Easily retains its status as my favourite Bond film.
Why? Loads of reasons...
It's got a wonderful Cold War spy thriller vibe. It's as close as Bond ever really gets to Le Carre - which, granted, isn't really that close, but still. That element of grit under the fingernails gives it a good, sharp contrast to the great, more fantastic elements of Bond, or the lighter stuff. The whole feel of the adventure is dangerous and top-notch.
The locations are smashing. From Istanbul to Venice, and they take the Orient Express. Wonderful!
The villains are perfect. Grant is a kind of anti-Bond, just as Klebb is Tatiana's opposite in every way. She's also one of the most hateful villains - quite thoroughly evil.
The wit, charm, humour - all present, never overwhelming.
As for Tatiana, she's terrific. I realised that I love this Bond girl for a couple of key reasons. First, the romance plot is handled remarkably well for a Bond picture - normally not that concerned with non-physical love. These two are spies, serving their countries, but we can really believe that the affection for each other are growing. They have little ups and downs - setbacks on the train, for instance, where James suspects her of being a double (triple?).
But she's great also because of her normalcy. She isn't an action girl - as fun as those are - or a femme fatale, but she feels more real. She has these great little touches - an easy example is her playing with her hair on the train, flipping it over her lip and pretending it's a moustache. Or when she kinda playfully calls James out for slapping her butt. These things feel like a real person with a life outside the film. Obviously not true, but I can picture Tatiana existing for herself outside of the plot. Most Bond girls are villains, seductresses, targets of seduction, action heroes, or some combination, but rarely do they have little quirks that make them feel like they might punch out at the end of the movie and relax at home. Tatiana has that.
There's lots more. The brutality of the train fight, the danger of the shoe-dagger, the gypsy camp sequence, or Kerim Bey's delightfully quirky self - I could go on-and-on.
But, for now, let's just say this is one of the all-time great Bonds - and my favourite - with (many) good reason(s).