A topic that I know something about! My wife is from an upper middle class family, and I am from a family that is quite poor. I grew up on food stamps, government subsidized houseing, and believing that everyone went to the food pantry. My wife's family does quite well - business owners that do quite well for themselves.
The main differences are sometimes subtle, sometimes not. One of the first things I remember being 'different' was manners. Around the dinner table, everyone would place a napkin on their lap to prevent spills. This was unique for me, because we couldn't afford cloth napkins. Also unique were things like thank you cards and annual holiday cards. Because it was another expense, we generally said our thank yous in person.
Sometimes I'll tell my wife about my upbringing, telling her about eating generic food (read - boxes of rice crisp's that were simply a white box that said "rice cereal" in black text.) much to her amazement. I tell her that we didn't have things like "snack cupboards" and I that I never really went school shopping. These sorts of things always seem to amaze her.
She tells me about the plays that she went to as a kid/young adult, annual vacations, and trips out of the country. She learned an instrument, had involved parents (read - free time), and generally quite stable surroundings.
Ultimately, I think that our different perspectives have helped us out a lot. I think that she has gained a lot of empathy, and I know that she and her family have pushed me to perform at a level I didn't have the confidence to until I met them. When I met my wife, I didn't have by bachelors degree, and questioned whether or not I'd ever finish. Being around them made me realize how important it was. Once I realized I wouldn't be able to work in my field without a master's degree, I went out and completed it in 3 semesters. I know that I wouldn't have been able to do it without their support.
I think we've both realized that people are more or less the same; however, confidence can be what differentiates you and can produce higher outcomes. It has made me realize the importance of intermingling socioeconomic classes, and understand just how dangerous it is that people see to be segregating along the lines of economic class these days.