What do you like best?
Gmail is pretty much the perfect email client, and I'm sure most of you have used it. Either for your personal email, work email, or school email.
Everything is customizable, which means you can make it just how you like it. You even get themes to customize the background and the text and stuff. They recently added CSS support for custom themes that you write yourself.
Google Docs is pretty much the only online office suite, so I can't find any reason not to recommend it. Good collaboration tools, easy to use, etc. It's a Google product, it works.
What do you dislike?
Google Code is being shutdown, so that kind of sucks for people who want to save those projects. I had to spend probably a month exporting projects and converting them to GitHub. Most of them are working properly, but unfortunately, some are having issues. This is a minor complaint though, since projects without any updates were most likely dead anyway. I did save all the Wii homebrew and emulators, which was the most important thing to me.
I don't use Google Calendar, because I usually just remember things. Heh.
But I must say, it is somewhat difficult to get use to and is a little convoluted. Getting rid of stuff posted by friends or stuff that Google just put there is also more difficult than it should be. Minor complaint, though.
Hangouts is OK, but for me I prefer Skype. Not really a dislike so much as something else is better. Google Hangouts would be better if it supported some of the same stuff that Skype does (file transfer, etc.). Minor complaint, more like personal preference.
Recommendations to others considering the product
I would recommend anybody switch to Google apps, depending on what you are switching from.
From any other email client, Gmail is such a breath of fresh air compared to Yahoo, Hotmail, Live mail, or AOL (yes, people still use AOL email addresses). It doesn't yet support some privacy and security features found in other, privacy-oriented email services. Google has said they will support some of those features in 2016, though.
I can't think of a reason not to switch to Google Docs if you have a business or something. I'm not really aware of any decent alternatives, and Google Docs is free and really flexible.
Google+ is eventually going to be removed from being required to use YouTube, so when that happens I will probably not use Google+ for YouTube. I will probably still use it for keeping up with some of my friends, since some of them are more active on Google+.
Speaking of YouTube, YouTube is probably both the best video sharing service and the one that needs the most work. It's great in it's ease of use, customizability, and flexible options are hard to beat. On the other hand, YouTube support is non-existent, and YouTube's DMCA take down policy/community guidelines policy is downright offensive at times. If you are coming from a lesser known video sharing service you should probably switch, but if you do, just be sure to have all of your videos backed up somewhere.
Google Code is being shutdown, but at the time, I think it was way better than CodePlex or BitBucket (I have used all of the services). Not much else to say, except switch to GitHub. I have a review of GitHub, which you can see here:
What business problems are you solving with the product? What benefits have you realized?
Businesses already widely use Google products, but if you haven't you really should.
The benefits outweigh any minor complaints that I or anybody else has.
You should switch, it makes sense from a business perspective because Google tools are very stable, and can handle many large workloads.
I use Google apps all the time and I have never wished I wasn't. If your company wants to increase productivity then you should switch. Not much else to say, really. :D