The LW 2.0 Open Beta is now live; this means you can create an account, start reading and posting, and tell us what you think.
Four points:
1) In case you're just tuning in, I took up the mantle of revitalizing LW through improving its codebase some time ago, and only made small amounts of progress until Oliver Habryka joined the project and put full-time engineering effort into it. He deserves the credit for the new design, and you can read about his strategic approach here.
2) If you want to use your current LW account on LW2.0, we didn't import the old passwords, and so you'll have to use the reset password functionality. If your LW account isn't tied to a current email, send a PM to habryka on lesswrong and he'll update the user account details on lesserwrong. He's also working on improving the site and sleeping and things like that, so don't expect an immediate response.
3) During the open beta there will be a green message in the bottom right hand corner of the screen. This is called Intercom, and is how you can tell us about issues with the site and ask other questions.
4) The open beta will end with a vote of users with over a thousand karma on whether we should switch the lesswrong.com URL to point to the new code and database. If this succeeds, all the activity from the open beta and the live site will be merged together. If the vote fails, we expect to archive LW until another team comes along to revive it. We currently don't have a date set, but this will be announced a week in advance.
We'll be doing a lot of work to optimize the site experience. (Right now, I don't have the sort of issues you describe, but it does take an unacceptably long time to load the comments on a page, for example). I expect some of that to help with these sorts of issues.
It wouldn't be practical to have the old and new sites running in parallel (they don't communicate with each other easily, they'd basically be two separate sites and part of the whole point is that this current site has too many underlying issues to make it practical to maintain), but if it's still having issues running on older hardware we may figure out some kind of "accessibility mode" that renders less complicated stuff, possibly with fewer features)
(I expect the people currently working on it to not get to that sort of thing for awhile because there's a long list of things that need doing fairly urgently, but it's worth noting that it's open sourced, so anyone who has time to fix an issue that's bugging them is welcome to do so)