For those of you anxiously awaiting the Boonex Dolphin 7 Release, the beta version was apparently due out June 20/21 2009. Boonex recently posted an update pushing back the Dolphin 7 Beta release to July 8th 2009. See this post for more details: D7 Update
The previously released Alpha version was intended more for just getting a limited look at Dolphin 7. I tested Dolphin 7 Alpha, and it is obvious many features aren't working yet, and many bugs and display glitches are present. But again this was just so the general public could take a peek at it.
Once the Beta Release comes out on July 8th 2009 hopefully a few more features will work and some of the bugs will be worked out. I honestly don't expect too much out of a Beta Release. Boonex Betas are traditionally very buggy.
In previous versions the first several Stable releases have a number of bugs and glitches. It's usually not until the 3rd or 4th release/update/patch of the Stable version that Dolphin actually becomes fun to use. So I am really not counting on it, or expecting too much for quite a while yet.
We really won't know until people start playing around with it. Hopefully most of the bugs will be worked out before hand. But as history suggests this will probably be awhile yet.
The good news is it is not going anywhere. It's better to wait until most of the bugs and glitches are worked out anyway. It will save you a bunch of time and headaches.
I would download and install it for testing purposes only. Spend some quality time really giving it a worked out, both beta and stable. After the bugs have been worked out, and you really have the hang of Dolphin 7, then I would think about installing or upgrading a live site.
Your members are used to your current Dolphin version anyway, so there's really no big rush or hurry. I know it's a hot topic lately, but do take your time with it.