I can tell you that the word "potluck" is actually a false cognate of potlatch, though the semantics have definitely impacted each other - see http://en.wikipedia.org/wiki/Potluck#Etymology.

In general, a contemporary potlatch would be easily recognizable as a potlatch to someone from before. For starters, the "Potlatch Ban" was only really handed down in 1885, and even then it wasn't enforced for quite some time. Even then, when it was finally enforced, most communities found ways around it, at least sporadically. The ban was rescinded in 51, meaning that there were many people alive who had not only participated in illegal potlatches, but many of the older community members had participated in potlatches before they were made illegal.

The potlatches I've been to compared to what I've read of older potlatches from authors like Boas suggest that by and large in most communities who potlatch, the form would still be recognizable, with the same songs, stories, symbols, purposes and so on being a part of the potlatch. The major differences would be in location (chairs and tables, usually in halls), and in level of participation (at least in many communities). In most communities they are now conducted largely in English, which is also a significant shift.

The ban did have a massive impact on traditional economic systems however. I do know that in many communities potlatches are important enough to play a serious economic role (with hundreds of thousands being spent on gifts and the like), they definitely play a smaller role than they previously did, especially as the main form of social gatherings. Things like community sports, birthday parties, fundraisers, and various other gatherings have stepped in to fill some of the gap, though - and this is just my impression - the potlatch ban in conjunction with residential school has led to much less cohesive communities.

I'm sorry, but are you saying it's illegal for a group of people to come together with various homemade foods?

As far as material culture, the songs, and dances go, I believe an 18th- or 19th-century NWC potlatcher would absolutely recognize a contemporary potlatch. Ironically the gold and silver jewelry that is so iconic in the Northwest Coast was only becoming widespread in the late 19th century. Influential Haida artist Charles Edenshaw (1839-1920) popularized both gold jewelry (carved horn bracelets were more common before) and argillite carving. He took traditional formline design in completely new directions that were rapidly adopted by many other artists and look "traditional" to us today.

The same can be said for the Kwakwaka'wakw Four (Chief George, Charley George Sr., Willie Seaweed, and George Walkus). They were active in the early 20th century, when the Potlatch Ban was in full swing and really kept mask carving alive. They were highly innovative, but their styles became widely adopted by the tribe and thus "traditional."

Chilkat weaving and ravenstail weaving are both enjoying a remarkable comeback since almost disappearing in the 1980s and 1990s. Ravenstail in particular is very conservative in design, so the robes and other gear would appear the same as far as colors and imagery, as a century or more ago, but the materials would be different (i.e. more sheep wool; less dog and mountain goat wool).

Feast bowls, cedar woven hats, carved dance masks—these are all flourishing and used in potlatches today, and the iconography remains the same (such as clan totem images) even if styles have changed.