Well if fighter pilots could bomb in WWII without bombing aids, I don't see why I couldn't in a 'Nam simulator.
By Vietnam you ought to have some level of computer assist plotting, at least for the dedicated strike aircraft. I know the Thud (do they even have the F-105?) and some models of the A-4 had a semi-modern system.
And as I've discovered I typically enjoy strike more than air-to-air in these games (I have since at least Falcon 3) so it's sort of an important point that the strike missions and aircraft be treated reasonably well.
Well, there are different variants of the planes and weapons from the years 1968 to 1975 available, so your bombing equipment depends on the year/variant.
If you're flying a Thud in 1968, it's unguided bombs and rockets only and bombing is a purely visual thing. On the HUD you get the gunsight that's either straight ahead for A/A or depressed by some amount for A/G. From what I read, in the real aircraft the amount of depression was adjustable by the pilot, so different setting for different weapons/airspeed/altitude could be chosen. But in SF2, the depression is fixed, so dive bombing is usually the easier choice. Level bombing is possible with some practice (more details here http://www.simhq.com/_air/air_055a.html
), but usually ripple-bombing or cluster bombs is the best approach. Hitting something small like a tank with a single Mk82 requires quite some luck... but then I guess that's realistic.
On the other hand, if you're flying a A-7 in 1975, you get a CCIP on the HUD and you have a the option of Walleyes, Paveways, Shrikes which have their targeting procedure modeled quite realistic. The red box in the screenshots is the "visual target" marker which is sort of cheating, but it's disabled when setting the game to "realistic".
@Icefire: I never played IL-2, so I cannot really compare it. But while the game is officially marketed as a "light" sim, I would put the flight model in the range of MS Flight Simulator, there's also the option of easy/normal/realistic for both the flight model, AI, targting systems, etc.
Graphic-wise, as you noted the planes are excellent, but the terrain is mediocre. There are also lots of third-party addons available (for example here: http://www.combatace.com/
), but I haven't looked closely at them yet.