I went through months of agonizing over what to do about the demise of iWeb, and ended up with something that's an improvement on several counts: Sandvox comes closest to iWeb's ease of use, but with several advantages:
Search Engine Optimization
Sandvox does Search Engine Optimization stuff as second nature, whereas iWeb wasn't SEO-friendly at all. It had been conceived by Apple as a sort of personal website maker before Facebook came out, and so SEO stuff was never built in. I've had MUCH better Google results since moving to Sandvox. The Meta Description is right there at the bottom of each page, waiting to be filled in. Tagging a page with keywords is simple, as is tagging photos with alternate text. Sandvox is set up with a dialog box to easily configure Google Tools and publishing a Google sitemap (the sitemap.xml.gz) is as easy as clicking a checkbox... only once, not every time you publish. These are all things that iWeb could only do with difficulty, using third-party software.
Here's the first blog post I did after going live with the Sandvox version of the Original Green site. As you can see, it has had over 2,500 readers and tons of comments. Both of these were high-water marks for the Original Green Blog. Before moving to Sandvox, each post would only rarely have over 500 readers. Since moving, 10 of 17 posts have had over 500 readers, with several over a thousand, and one more over 2,500. And nearly every post has more commenters than typical posts before the move.
Layout
At first, the Sandvox layout seems to be a bit of a downer... iWeb let you move text and graphics all over the page, like a page layout program, whereas Sandvox is more restrictive about how and where you place stuff. But iWeb sites often did very unpredictable things on different machines and browsers, whereas Sandvox sites are far more predictable... so the restrictions are a blessing in disguise.
Community
Karelia has an active user community like Apple's iWeb community, but the difference is that whereas Apple never talks about future products, Karelia's engineers and even their owners are heavily involved in discussions of where to take Sandvox. And they listen. Already (I've only been using Sandvox for 6 months) they've implemented several changes I asked for.
Versions
These changes come quickly in the form of new versions, especially if you choose to take part in the beta program. No waiting a year or two for upgrades, like we did with iWeb.
Collections
The mechanism Sandvox uses for blogging (a "Collection") is extremely versatile. Basically, you can use the blog mechanism not only with a collection of blog posts, but with a collection of project pages, tool pages, book pages, services pages, product pages, plan pages... whatever. If you need a cover page and several detail pages within it, either organized chronologically or alphabetically, this is a really nifty feature. I blogged more about Sandvox collections here.
Templates
Sandvox is much more nimble with template pages of any sort. Just set the page up the way you want and click Draft (do not publish.) You can now duplicate your new template anytime you want a new post, detail page, or whatever. Also, unlike iWeb, you can duplicate an entire collection if needed. Better yet, you can even drag and drop pages or entire collections from one domain file to the next. For example, I could copy my entire Original Green blog to the Mouzon Design site if desired just by a quick drag-and-drop.
Publishing
Publishing in Sandvox is easy and clever.
Sidebars
Sandvox's sidebars are a huge time-saver.
Objects
Sandvox has a lot of built-in Objects, from raw HTML objects to Amazon lists, Facebook buttons, contact forms, Flickr thumbnails, lists of external links, page counters, Google maps, Twitter buttons, YouTube content, etc.
Favicon
It's easy to create a favicon for your site... you probably know already, but a favicon is the little icon that occurs in the URL line of your browser for each page of a more sophisticated site.
Comments
iWeb used its own blog comment system, but it was quirky and when something went wrong, it was usually impossible to fix... the comment was gone forever. Sandvox, on the other hand, has built-in support for several comment systems. I use Facebook comments, and to great effect because it drives many people to my sites that would never have known about them otherwise. When one of my Facebook friends comments, it goes on their timeline and all of their friends have an opportunity to see the comment and join the discussion. If each has 500 friends, then each comment on my site reaches close to 500 people I don't know, assuming we don't have heavy friend overlap. And you can put Facebook comments anywhere you want, not just on a blog post. Matter of fact, I have a comments module at the bottom of almost every page, because I want visitors to have the opportunity for a conversation about my entire site, not just my blog.
There's much more, but you get the idea... leaving iWeb seemed really painful at first, but it's been one of the best changes I've made in years to my internet presence. Here's a page that translates between iWeb and Sandvox, so you can quickly figure out how to do what you were doing in iWeb in Sandvox instead.