A couple of thoughts (It's not something I've had to do)

Wouldn't you make the links on the navigation menu no-follow?

I'm assuming that you don't want search engines to index your members only content.

You don't want the members only content ranking for keywords do you (and if it's not being indexed then how can it?)

Would it not be an idea to try any get some value out of the inbound links by using 301 redirects to relevant indexed content when the user is not logged in?

I don't know what type of site/services you're offering, but if people following these external links to your member only content are potentially customers then it would be worth presenting them with a page that reassures them that the content they are looking for can be found within the site, present the benefits of becoming a member etc... Even better, If you can make the appeal relevant to the content they are trying to access.

Interested to find out what everyone else does!

In my experience, especially if you've got a content rich site (and I'm assuming you do as you mention a two tier bar), getting the information architecture right first is absolutely essential You should be fitting the navigation around the content - not the other way round.

I don't know if you're able to modify this architecture. If you can then you need to be a little bit cautious. Make sure that you test any changes with members of the target audience. Make sure that if there are any changes to URLs (renaming sections etc) then you create suitable redirects. Don't ignore testing your architecture!

Make sure that the words used for each item provide the visitor with a clear understanding of what they're going to get if they click on the link. Don't use generic words/phrases like "articles"

Can provide incentives/compelling reasons for people to want to explore sections on your site? This will depend on the nature of the site of course. Don't over-do it though.

The entire Navbar should provide the visitor with a clear overview of the scope of the site. It's probably the first thing they'll see once they arrive and you want them to be able to quickly scan it and know that they're going to find what they're looking for. (Information scent)

Make sure that the Nav bar clearly indicates the current page/section to help the visitor know exactly where he is.

Use words on the menu bar that are going to be meaningful to visitors. Avoid jargon and acronyms. Try to take an external perspective. This is where keyword research can also help! The words you use should tie in to your keyword strategy and audience.

Think about how your navigation can reflect your brand and credibility.

What were the particular issues you face with the current navigation. Can you provide more specific detail, examples or the name of the site?

What were the reasons for choosing a two-tier approach?

Hope this helps!

It's probably a bit of a balancing act. The advantage of using web fonts is that it makes the text that you would have "hidden" in images accessible - goof thing for SEO if the text includes keywords and/or describes the content.

As you say, the downside is the additional load time. This depends on the particular font and of course where it's hosted. I've used the google hosted fonts on a project and not had any significant problems with speed.

Speed can be a red herring though as you would have had to download the images before. If you're replacing lots of images with web fonts then you may actually be delivering fewer bytes.

Perception can be different though as the browser has to download the font before it can render the text.