History:
Started seeing this guy for most of year, heavy dating for past 6 months.
What he's like:
Intelligent, attentive - mostly, type AAA, smart-ass - but like that

- caring, mostly considerate, lovable.
Things that make me wonder
Type AAA, self-centered, did nothing for valentine's day, forgot birthday (July) when I thought would never forget (did little to make up for it)...but most relevantly, seems to leave me hanging out to dry in little ways that has me questioning what would happen about big things.
Any thoughts?
Just some comments for you to ponder:
Having dated for a long time before getting married, I discovered there are people who focus and make a big event on certain dates/events and others who don't. Some of it is cultural. Some of it is personal. Just because someone doesn't do anything on a particular day does not mean that they don't care. Try not to equate the two.
Take birthdays for example. If the person "forgets" yours (or more than likely doesn't celebrate them) you can easily see the same when their birthday comes around. Do nothing and you'll find out.
Heck, a long time ago, I dated a lady who decorated her place, made a cake, invited close friends, and many other things for my birthday. While it was nice, I did not enjoy myself at all. It was way too much for me. I prefer a simple quiet birthday. No gifts needed or wanted. And if we decide to do something special such as dinner the event can be on the weekend instead of on the actual date.
Now please don't take this as condoning his actions. He sounds like he is a bit self centered and that is bad for any relationship. Then again, I've dated women who after I spent a weekend with them I needed a vacation because they required so much attention when I was with them. Sure glad that I didn't end up with one of them as my life would be hell on Earth.
Someone once told me these wise words about marriage.
Men get married expecting women not to change...and they do.
Women get married expecting to change their man...and they can't.
As they say love is blind but marriage is a real eye opener!
Basically, in a nutshell, you have to accept the other person as they are. And if you can't, then they are probably not the right one for you.
Now I realize that you are just dating at this time, but usually most people date with the possible future of getting married to the person. If this is the case, then my comments above may help you out.
If you are just dating to have fun, then if you are not having fun, exit the relationship. There are so many other guys out there why waste time with one that you don't enjoy.
Hope this helps a bit.