Hi guys, this is more feedback than anything else.
Traditionally, before WPMU we were using CometCache Pro for caching which is a really awesome plugin.
But seeing as we subscribe to WPMU, we figured that we may as well check out Hummingbird. Initially we found it really good and it did a great job of caching and speeding up the site.
However we found over more and more sites, that it was breaking the styling on the site and often displaying a non-styled page. Unfortunately, this was not always obvious to us as we had locally cached pages, or were logged into the site already – or we were just on a homepage, or not incognito.
But we started getting complaints form our SEO team, or worse the customer, and we started noticing that this was happening on a multitude of sites (we had over 50 websites running it at the time). It was quite apparent immediately that there was an issue with the cache. Clearing the cache fixed it initially, but even as soon as the next round of caching it was broken again.
We have had to remove Hummingbird and stick CometCache Pro back on all the sites, as it affected more than half of them that we noticed, so made the exec decision to remove it asap to prevent further unhappy clients.
A few things to note: We were running the latest versions of plugins and the WP installation. The sites varied a lot between each other – some had a few plugins, some had quite a few. The main plugins we generally use on all sites are Advanced Custom Forms Pro, Gravity Forms Pro, Yoast, WPU Dev, WP Smush Pro, Defender Pro. Then some others depending on what is required. I've always believed less is best when it comes to plugins, so I don't like to overload them.
Anyway, I'll leave that as food for thought. If it was 1 or 2 sites, I probably wouldn't have bothered to write this, but 25 affected sites (or more), it becomes an epidemic.
Hope you guys have an idea, and maybe we can look forward to a more robust version in the future.