When I bought the bike, I knew it would need new tires. Got a Dunlop front on sale for $45 and the rear for $120, 30 a side to install, pretty reasonable for tires.
Speedometer and odometer quit because front wheel bearing went bad and shredded the plastic gear; $25 part with $30 more labor to replace.
Missing one reflector and chrome swingarm bolt covers (extremely minor and hard to notice these things).
This is a great motorcycle, very comfortable and easy to ride, but with plenty of power for just about any situation. The engine is very tractable and hard to stall and has nice progressive clutch feel. If you should end up in the wrong gear for the situation, it usually doesn't matter because the engine is so torquey. The transmission is also easy to find each gear and neutral with, if a bit clunky overall.
It's also an extremely reliable bike; it starts perfectly every time, even when sitting out overnight in the near freezing temperatures. The materials used are all extremely high quality and easy to care for, making for a bike that's 18 years old, but looks and rides like a 2 year old.
At nearly 500lbs with a full tank, it's not the lightest bike in the world, but very easy to balance at low speeds and roomy enough for a 6' rider like me to fit comfortably. It also handles better than you'd expect from its specifications, and will let you have some fun in the twisties. The previous owner added a Spitfire windshield and custom highway pegs, which also make it nice for long trips too.
The only real quibbles I have with it are general stock/naked bike concerns. The suspension is pretty soft and not the most responsive, though comfortable for cruising. The stock seat could also have a little more padding, but it's not a crotch mangler or anything like that. Finally, it would probably handle better with a fatter set of tires, the stock ones are fairly narrow, but the low cost of replacing the stockers is pretty nice. Even with the windshield the wind does make it's presence known at higher speeds, just hang on tighter and remember how much it costs to replace plastics!
Overall, I don't think you could really go wrong with a Nighthawk 750. I picked mine up for $2000, and it's been a complete joy and very adaptable to many situations.