The film's Bond Opening is extremely different than a normal opening as, instead of erotically dancing women, it's full of an animated Bond fighting off Mooks. Fighting off bad guys to save the world is the archetypical spy fantasy, which an inexperienced Bond would've thought when he was recruited. Also, only one girl appears in the opening - Vesper. Her betrayal and death is what spurned Bond from romantic attachments, making him the playboy we know him as. It doesn't help that she's briefly seen in the aim of a crosshair.
Another from the opening: the part with the two holes being shot in the 7 card leading into "007 status confirmed". Not only a cool moment but symbolic of how two shots allowed Bond to become 007.
The opening theme itself seems to plainly support the idea that 007 is explicitly a role to be filled rather than any one agent, as had been suggested over the course of the film franchise with its different actors all playing the primary character. The chorus line is a statement that while Bond's work is important, it will be mostly thankless and unfulfilling, it will be dangerous, and if he dies he will be replaced by someone else, with the secrecy of the job meaning there may not even be anyone to mourn him. It's fitting that he'd get this kind of talk while he's relatively new on the scene to make sure he knows what he's getting into.
Dryden taunting Bond about how difficult his first kill was—"Made you feel it, did he?"—and how the second is easier. Bond agrees after shooting him. Bond's first kill was a knock-down, drag out fight that lasted relatively forever and culminated in him drowning and strangling the guy, and even then, he still wasn't dead. His second involved him simply putting a bullet into his target. Of course it was easier.
The spy gadgets in this film are rather more low-key than in previous iterations of the franchise, but instead are tend towards more-advanced versions of Real Life technology such as cell phones (Bond's is able to follow a tracking device being tracked by Spy Satellites) and automatic defibrillators (his fits in a hidden compartment in his car's glove box, and can be connected to the aforementioned phone to allow Mission Control to run diagnostics and check his vitals). This is a subtle Lampshade Hanging about the more advanced state of technology and how many traditional spy gadgets would have been rendered obsolete. After all, who needs a shoe phone when a normal phone is smaller and would draw less attention?
When Bond and Vesper first meet on the train, Bond makes a remark that Vesper isn't his type. She asks if it's because she's smart, and he replies it's because she's single. In the end though, they still wind up together... until the finale, where we find out Vesper had a lover who was being used as leverage against her. She wasn't actually single at all, which is possibly why Bond fell for her.
When asked by Bond about the winnings, Felix Leiter's "Does it look like we need the money?" sounds badass at first. It then hits you that it's U.S. taxpayer money that got lost in a fell-swoop plus Leiter even failed to catch LeChiffre after Bond won. It just cements Vesper's fear during the train conversation: without Bond's luck and skill in poker, the U.S. indirectly financed terrorism.
Vesper casually states that MI6 prefers to recruit orphans without stating why. The implication is that with no family to have emotional ties to, a potential Double-O Agent not only has no worries about them being kidnapped and used as leverage against them, but he also sees MI6/England as a substitute parental figure.