What do you like best?
We're a heavily Microsoft-centric office, so this one's tough. The basic work suite, especially Word and Excel is a necessity, and the current offering of the 2016 apps do their job just fine, so I'll ignore those as part of what I like best.
I think that the choice to use either the fully installed app (suite) or the online versions of the apps is a really big plus, and possibly one of the biggest selling points of the subscription. We've had some major policy violations at the office with employees sharing sensitive customer data via unprotected Google Docs, to the point where we had to essentially completely block google docs, so Microsoft's options in locking down sharing methods is just plain awesome. Although the battle between Google Docs and Office Online rages on, I personally think the Office suite is a more professional solution (once you have the online sharing figured out, more about that in my dislikes).
Being on the E3 plan also gives us access to many other apps, many of which we don't even need. Teams, which I've also reviewed, is used throughout the company now. There's an app/interface called Delve, and to be honest I don't know what it does. Our collaboration centric employees however have all taken to using it, and I wish I could explain a bit more about what it does. However, when employees take initiative to start using new software on their own, that's usually a good sign, so I thought I'd mention it.
Support has been a bit slow occasionally, but they've come through on every issue so far, so I'd have to give them a thumbs up.
What do you dislike?
The implementation was a bit rough. We're a pretty tech savvy bunch in our IT team, and it seemed that we weren't really able to launch ourselves without working with a 3rd party account manager. We had a few conference calls, which we only had to get that checked off the list, they gave us what we needed and we were off.
After a few expected hiccups we ran into some features not working (say collaboration in Excel Online), because we were on a version and build that did not support it (and we were on the regular release schedule) even though this feature was heavily advertised. After plenty of research we finally figured out that Excel Online Collaboration only works as of a specific version, which is only pushed via the fast ring/monthly updates. The documentation on this was severely lacking, and we had some execs breathing down on our necks because they followed technet guides on their own and it was simply not mentioned anywhere.
The above, plus Teams feeling like a Beta with frequent issues, are the only notable issues. Having experienced similar rollouts I feel it's within the realm of a pretty standard rollout, maybe slightly on the rough side.
I can't get through this without mentioning that I hate Sharepoint. Yes, Sharepoint still exists, and it's part of Office 365. I've successfully managed to avoid any interaction with it so far, and this is aided by the fact that MS appears to have made it simple enough for users to manage their own Sharepoint sites now, and to me, that is a victory. I guess maybe that's a positive. Either way, keep Sharepoint away from me please, thanks.
OneDrive is just ok. I'm a big Dropbox fan, and OneDrive does seem like a pretty big step down from that. Maybe that's just me, but Dropbox just has the process and ease of use down. However, in OneDrive's favor, it integrates beautifully with the rest of the suite and does it a better choice, regardless of my preference. Again, another plus/minus I suppose.
Recommendations to others considering the product
Stick with the setup even if you hit some roadbumps, it's worth it.
Make sure you can make use of a lot of the offerings of the suite outside of the basic Office Apps, as that's where the real advantage lies. Let your users explore a bit, you might get better feedback from the switch than you expected.
What business problems are you solving with the product? What benefits have you realized?
Moving away from Google Docs was a major accomplishment, since controlling who shares what is a nightmare when everyone has a Google account of one form or another and shares things via their own account like their life depended on it.
Everything being hosted online also opens the door to on the fly management via their admin app, which I didn't particularly have knowledge off before we jumped right in, but it's plain awesome. I personally detest having to RDP from my phone into my office machine (personal preference I guess), but that was commonplace if it was outside work hours and I had to make a change in, say, Exchange. With the admin app, this eliminated the need for that almost entirely and changes are fast and easy.