Re: My sister wants to marry...
I'm a little disturbed by some of the replies here, so let me give you my two cents, from the guy's perspective.
First of all, he converted well before marriage, so you can't question his faith. In my experience, most converts tend to be more seriously practicing than many born muslims. This is somewhat different for those who convert just to get married.
If your sister and he are both religious, there shouldn't be any major cultural differences. My husband and I don't have any, because when we have an issue that we absolutely cannot resolve we immediately look at what Islam has to say about it. This has happened maybe a handful of times in the past 15 years.
In a lot of mixed marriages, the dominant culture tends to be the one that is the most "overwhelming", if you know what I mean. Desi culture is definitely this. If the boy is American, then American "culture" in individual families is very flexible, allowing for new things to come in to it without any period of adjustment. I know both American men married to Pakistani girls and many American women married to Pakistani guys. In both cases there is more Pakistani food cooked in the house, salwar kameez is worn on Eid day, and more time is usually spent with the desi in-laws.
By the way, marrying outside of your culture is a sunnah, something that the Prophet (saw) did in several cases and also something that he encouraged.
It depends whether your sister cares more about culture or Islam, and whether your parents care more about culture or Islam.
Even non-muslim goras don't go into marriage thinking that it won't be a life-long commitment, a convert to Islam will take those vows very seriously, and if he is a practicing brother, your sister will receive the full rights that Islam has given her.
An added bonus for your parents should be that she won't have to put up with nosy, picky in-laws who make trouble for her, or people trying to cause problems in her marriage. Even parents of converts I know who were not happy that their child converted have been accepting and loving towards their families. Many go so far as to send gifts to the kids on eid and so on. Her in-laws will most likely be very loving and will go out of their way to make your sister feel welcome in their family.
That said, the biggest problem in your sister's marriage, from my and other's experience, is most likely to be you and your family. Desi families feel a need to interfere in every small detail, whether it's their business or not. Are you willing to accept him as he is, or do you want him to "act like a Pakistani"? Are you willing to trust your sister's instincts, or will you second guess every move she makes and then say - "see, this is what happens when you marry someone from another culture?" The divorce rate among mixed couples that I know is fairly low, certainly no higher than with desi couples living in the US, where divorce seems to be a new trend.
You have to be open-minded and accepting of him and his family as well. There's nothing unislamic about inviting non-muslim relatives to your home once in awhile - many families of converts are so put off of Islam because of the way they are treated by muslims.
In the end, every marriage has some problem or other at some time or other (check out Life1), but it's apparent that your sister puts more emphasis on her faith than her culture, so you and your parents should trust that and do the same.