At least on google+ they didn't just remove the ability to reload. They replaced it with the ability to go back to the top of your stream without reloading everything.
Since google+ already loads new posts automatically. This has the same practical effect as before in most cases. But with the advantage of faster loading since it doesn't reload everything because it doesn't need to.
With the "Kennedy" UI (codename for the recent cross-product redesign), many Google properties had their own logo replaced by a plain Google one. Now, to differentiate between products such as Google Voice, a red-colored product name is displayed right below the Google logo.
Also, when you do a Google search, the product name is now always "Search", even when you started a search in Google News / Images / Videos / Shopping / Books / Places / Blogs / Discussions / Applications / Recipes or Patentes.
With Kennedy, Google has actually reached its goal of becoming a 'universal search engine' and it can finally show a single interface for (almost) all types of queries (except for Maps, Flights and search for personal/private items like email and documents).
You can still access the specific homepages of Google Images and Google News, but Google is slowly convincing users to initiate all their searches from google.com, without thinking about which engine to use. Thus, every search from news.google.com redirects to classic google.com, with the "news" filter activated.
For personal searches (eg Gmail, Reader, Docs, Voice), Google hasn't completely switched to the "filtered results interface". Most of those apps need their own homepage with a list of items (messages, contacts, documents, voice messages, top stories, feed items). However:
- most of them have switched to the plain Google logo with the red-colored product title. You can stay in the app or refresh the item list by clicking on the product title instead of the Google logo, which would lead you to the unexpected Google homepage;
- most of those homepage (or "item lists") could be merged with Google+ and the new notification bar on google.com, so you could access all your personal things from a classic search. For social results, it's working pretty well since Google Plus Your World: all social items are shown on-top of other results in a classic search. Soon, every new email, documents update or voice message could appear in the notification bar and search results (just like social items): no need to go to mail.google.com, docs.google.com or voice.google.com.
Now (to answer your question), what result do you expect from a click on the Google logo in Gmail? - To go to you inbox? No, that should be the result of a click on the product title, Gmail.
- to go to the Google homepage? No, you're not familiar enough with Kennedy navigation.
So my guess is that Google is trying everything to get you to click on products' title to go to/refresh its homepage. Meanwhile, they prevent you from clicking on the Google logo because you wouldn't understand (yet) why you would be redirected to google.com from Gmail.
If this (presumed) strategy work, you would always go to google.com to interact with any kind of products/items, without having to "navigate". Just search Google or browse your notification stream, whatever the type of content (message, documents, web pages...) and its context (personal, social, public...).
Just looking at Gmail now, there actually isn't a Gmail logo anymore. There is a Google logo that I can't click on and there's a Gmail link underneath it, but clicking the Gmail link opens a popup menu. I have to then click "Gmail" on the popup menu to get to my Inbox. (Or I could just click "Inbox" of course, but that sometimes gets hidden when i have a lot of labels open, and it's a smaller, fiddly link). I'd bet more people will have noticed this change in behavior than those who've noticed the change from a Gmail logo to a Google logo.
My point is, all this requires me to think. But before I could just swing my mouse into the top left corner, click "Gmail" and always end up at my inbox, no matter where I was in the application. This consistency has gone.
I should have phrased my question: "What possible advantage does this offer, to the user?"
Ah, I knew someone would mention the total inconsistency of Gmail's title. I also think it's detrimental to the vast majority of its users.
For most other products, Google prefers to frustrate some users (cf. https://plus.google.com/117598418867899518106/posts/Zr4vhv6p...) by disabling all logos' links while users get familiar with clicking the products' titles to go to the products' home. But once users will be used to this and all those products will be fully integrated with Google Search (cf. my previous comment), then they'll add a link to the all those Google logos in products' header because they won't be lost in a service (Google Search) that is independent to the product they come from (Gmail / Docs / Reader...). If they succeed, I think all users will benefit from this new navigation concept.
I don't like the current situation (unusable product logo) but it's certainly temporary: they've reverted to the dark navigation bar a few days after the release of the big toolbelt navigation menu, so they're probably still looking for a good solution.
In the meantime, it's a difficult POLA dilemma (http://en.wikipedia.org/wiki/Principle_of_least_astonishment): 50% of Gmail users might expect to be sent to Google's homepage by clicking the Google logo in Gmail, while the other users might expect to refresh Gmail or go back the inbox by clicking the only logo in Gmail's header. Where should Gmail's Google logo point to?
