Just guessing , but I'd say the hardiness issue is a concern in zone 6, and some sources go as far as saying they're only dependable to zone 7? I will admit, though the rarity of certain plants in your area may just be a matter of folks not having tried them or even being aware of them if they're not offered by local sources, but usually just looking around a neighborhood or area in general and seeing what plants are growing well there, can indicate what's hardy or not! If local sources don't offer particular plants , it's usually an indication they're not hardy for your area. Meanwhile , hopefully some other folks in your zone will answer whether they've tried them and how well they've done long term, for a better answer!
I must say, seeing how pretty they are, I've often been tempted to try them in my zone 5-6 garden, but that would be pushing things most likely!

Sorry I didn't see this post earlier ...

check out this site .. I don't know if he has any left, but I fully intend to put them in next year to cover a wooden swing frame my grandkids have outgrown. This nursery is located in Zone 6 and ... well you can read all about it..

http://www.carrollgardens.com/gardenclub/?p=730

Carolina Jessamine is ROOT hardy in Z6. But, it is a spring bloomer on old wood. I often had no blooms just south of DC for the CJ that was not in an exposed site. And I lost most of the top growth every other winter. The one that bloomed was behind a fence on a south facing wall. I was 40 miles south of Carroll Gardens in Zone 7b. That said, I understand the lust for marginal plants.

I intend to try this one. It is a NEW variety that has just come out this season(2008). It is not the standard Carolina Jasmine. I lived in Texas for years and grew it there, so I know it's hardiness. The only way to know about Margarita is to try it.

Sorry I'm happening upon this so late in the game, but I've been growing this in a very protected location for several years now. What everyone said is right--the roots and even some of the top growth survive our winters, and if I'm lucky and run out into the cold at just the right time, I might even spot a flower. Maybe. I've discovered that surviving...as in clinging to life...and actually flourishing are very different things.

Sorry to have seen this so late. I found the link while doing a google search to try and find the botanical name of the great hardy yellow-flowered jasmine vine in my garden.

This is definitely it. I bought the plant in the spring of 2005 (mail order - I'm guessing from the now closed "Flower Scent Gardens") and this is the first season that it's really come into it's own. It was covered with 1" yellow flowers for about 3-4 weeks in May. They're not very fragrant, but they're beautiful and bright (I'm hoping the frangrance will increase with age) and they last for a very long time floating in water.

The vine is rather restrained (only about 6'), but the foliage is bright and clean. It takes on a bronze hue in colder weather and it behaves as a semi-evergreen in my garden. It does NOT like to be pruned.

Overall, it's been worth the wait and I LOVE it!

Even later yet in response, but I am enthusiastic about Gelsemium sempervirens and have had one that has been trouble-free, extremely vigorous, beautifully blooming, for a short period, and mildly fragrant. The fragrance will not increase unless the flower count does. As with Long Island, the ocean affects my climate, and Winter does not get as cold as areas to my West.
Unfortunately, nurseries do not always stock plants suitable to their zones. This is notoriously true of what are called 'box stores'. You can find some unusual stuff, totally unsuited, with some very uneducated staff.

even later to the party... found it in a local nursery in CT/zone 6... decided to try it. Glad I found this thread because now I know not it may not flower well for me if it gets hit hard. I'll just have to wait and see. It had struck me odd as I had never seen it before...that should have been a signal don't buy don't buy but I just had to try it.

I have several. The oldest is over ten years old and is totally hardy. They are all the "Margarita" variety though, so that is significantly hardier than other types. It is covered with blooms every year and is now well over 15 feet spread along a fence which is atop a wall. The overall height is at least 10 feet and then it spreads along the fence. I have two others which cascade down a stone wall and are 5 years old. They reach the ground 5 feet below and spread a bit. All of them are totally hardy, even on the windy hill on which I live. The first one was taken three years ago and this one is now twice the size. The second one is two years ago and that one has reached down to the patio below and spread also. They are totally hardy here, evergreen every year and virtually no leaf burn or damage ever. I love the flowers, but I have not noticed any fragrance.

No fragrance on 'Margarita' variety?