Diigo

This review has two parts, positive and negative, but it is mostly lean towards negative side for apparent reasons.

Positive:
Diigo lets you:

• have multiple colors in your highlights
• have private or public annotation
• organize your bookmarks in your profile
• have native browser extensions (good bye bookmarklets)
• have native Android app
• cache web pages to have what you annotated regardless of the website's update
• take screen captures
• share your annotations with a group of users
• annotate PDF from your web browser and save it on their server (PDF + annotations)

Now the negative side which forced me to stop paying them to be a premium user:

I used it for about a year or more and I was a premium user, the site was mostly functional and it was growing with acceptable pace until December 2014 that they announced a feature called "Outliners" as a new version of the features they had as "Lists".
Outliners were (and at the moment are) very buggy, ugly and in practical as you can see in the following forum discussion in their website support section:
http://feedback.diigo.com/forums/76211-ideas/suggestions/6803419-make-outliners-optional-and-return-lists-as-option

Here are the reasons why I say Diigo support team is bad:

• Dictatorship: The Diigo team forced users to switch to Outliners. This caused loss of user data and annotation order.
• Irresponsibility: Users (mostly premium users) asked Diigo to let them know about the progress of developing Outliners but they never replied (refer to the discussion link)
• obstinate: stubbornly refusing to answer users, stubbornly refusing to read users suggestion to ease the conversion and progress of moving to Outliners. (refer to the discussion post)
• Poor support: every few months, they add a feature to their website and specially the Outliners section but bug reports are piling up without any action taken by the devel or support team.

The hilarious part was premium users was paying Diigo and also trying to work out a solution and designing new features for FREE (!!) and yet Diigo team was just ignoring them and draining money out of our pockets.

Currently I'm trying to test multiple other services:
Hypothes.is
Annotateit.org
annotary.com
Scrible.com

The first two are lacking so many features and extremely ugly. The two latter ones are more closer to Diigo concept and so far I'm trying to decide which one is better to stick to it.

I LOVE what this app can do. You can put sticky notes on sites for other Diigo users to see while browsing, you can store graphical and HTML versions of each site you bookmark, you can share via many different methods, you can highlight and share annotations. . . . Just really cool.

THE ONLY THING IS, seems like a very small groups of people support this app and it shows when something goes wrong. I've only been using this for two weeks, I have to say, for what it's worth, but when e-mail functionality seemed to go down, no one responded to my questions about it (via Twitter, forum, and e-mail) and it remained down for at least 36 more hours.

Because it is just so frigging feature-rich and ahead of everyone else I've looked at, I'm going to stick with it for a while and see how it goes.

I love this app - i can tag links at work to look at later at home; i can share links with people ro keep them private; I can make notes with powernote on my phone and then view them at work. You can even make sticky notes on a webpage (though I've not done that yet). It is basically like a much more powerful version of delicious.

Only problem is that it does occasionally go down and there is never any reason why given

Better than delicious, it have the "read it later" function, highlight too is usefull, and I very like the possibility to read the rss feed for a tag, that allow to see the most recent bookmark about a tag.

I have been using free version for 9 years.
Unfortunately there is no free (windows + android) alternatives with better features.