I posted my rules mods for the new edition/remaster of Dungeons & Dragons a ways back. Since then, I've put 10 or so sessions on the tires (and brought back proficiency, lol), about 50 hours, mainly with my core group (now called THE SKULL SEEKERS) who just finished their 60th session.
I am quite the outlier on this rendition of D&D, in that I love the new books and the refinements therein. I don't think the reader need endure another review or overview of the PHB, DMG, and MM, (ahh, the trifecta!) but I wanted to take some time to talk about real, at-table aspects of 5.5 that are reminding me, unpopularly, that D&D really is the iron horse. The OSR, if indeed an identifiable thing/people, doesn't want to hear this, but the RPG that started it all is running better than ever, and can't be pinned down to any style.

5.5 has its critics and its fans. I, dear reader, am the latter.
1: Depth is Still Dope
The rally cry of 'rules light' has certainly captured my heart over the years, as is well-documented in my work and game groups. I spent 4 years in OSE, threw down with DM Scotty to refine and complete EZD6, and most notably published ICRPG (sorry for all the acronyms, I'm on a roll here). We've all felt the amazing rush when rules complexity is tossed out for creative, fast play.
Despite that intro, as you have predicted, I'm here to also report that depth and 'crunch' and absolutely awesome. The magic is still there.
So often we see talking heads online criticizing WOTC D&D for too many bonus actions, a too-lengthy death sequence, overly deep enemies, power creep, too-large numerics, and dear-gods-is-it-still-the-wizard's-turn spell texts. I can handily, with total certainty say that these hot-takes are all shoe glue, and hold no real weight with a regular group.
Bonus Actions: They're great. Hero coins and other parachute mechanics are more durable. Good players have these on command and they use up next-to-zero table time, while adding a kickass 'pinball' vibe to the occasional turn.
Death Saves: I don't know how folks are doing things that they think D&D 5.5 is too easy or not deadly enough. We lost a character against 6 Barbed Devils. It was brutal. We have heroes down or near obliteration every session.
Deep Foes: The new MM is best-ever (besides the early 80s 'roster' style listings) for stat blocks. The improvements remind me, again, that complexity and depth are actually cool when deployed smoothly. Stats 'n Saves next to each other? Divine. If you really know the many monster books in all of role playing, you can't deny that the wording refinements here are very, very good for the DM.
Power Creep: We divide all XP take by 10 before tallying session value. Creep solved.
Big Numbers: If 40 is vastly more complex that 4 to the reader, I could see how 5.5 is an irritant. We have found that things play out in a very AD&D-harmonic way, just at an exponent up. It's a thrill to do 35 damage rather than 4. Is it substantially different? No.
Spells: I don't know about the reader, but I think the new spell section in the PHB is solid gold. I'm seeing dividends in 5 classes so far, with Sorcerer being my favorite as far as cleanup. Meta magic especially is finally easy, fast, and intuitive (why always Kenku, though?).
Long story short, bring on the depth. I'm officially taking a well-earned reprieve from rules-light. At this level of clarity, the depth deploys really well.
2: Old and New Are Both Illusions
The reader may have seen my last blog, using 5.5 to run Caverns of Tsojcanth (Gygax, 1982). This session reminded me of something I think we'd all benefit from remembering and repeating: stereotypes of what is old and what is new are BOTH WRONG.
It's hard to create a thumbnail these days that gets traction. Sadly, this mindset has caused a cognitive decline that over-broadcasts provocative hot-takes. Sorry, algorithm, the imaginary scandals and 'this one trick' garbage don't ring true in the realm of the actual. Players and DMs are vastly diverse BLENDS of styles, interests, and themes. Despite what the OSR is telling you, there was color art in the 80s. Vintage modules are cool, but also horrible in places. New D&D can be colorful or even whimsical in places, but also has some amazingly grim imagery in the DMG and MM.
Want to have more fun with your role playing hobby? Let go of generalizations. Just be. Little bit o' dis, little bit o' dat.
3: Using CR is Brain-Butter
Another big poo-pile we often hear is how 'broken' or terrible CHALLENGE RATING is. Sure, the provided XP-based system is spaghetti, but the number as a general reference is still fun, I say! Still fun!
Ok, it's NOT FUN to use it as a precision caliper. But as a "we took down 5 CR 6's?" or "it was 30 total CR!', what was derided as a cumbersome formula becomes a very handy measuring stick. Don't expect to achieve 'balance' with CR. But if your homie sends out a CR total 4 encounter and the group wipes, while your table rocks CR 50 with a ragged 3-man, you can brag with numeric precision. This is brain butter.

The sublime joy of rolling a nat 20, especially when it's your only chance, endures in 5.5 as ever.
This core truth may be obvious, but it bears repeating. Traditions hold strong and true here.
4: No Style
Here's my biggest and juiciest bit. Despite the endless obsession of so many to find the coolest book, setting, or rules core, D&D 5.5 has no prescribed or enforceable style. It can dungeon crawl with 3 HP with the best of 'em, clash with immortals and level 18 insanity, burn torches in real time, or goof off in a tavern. You can run horror, pulp, whimsy, Pokemon, death metal or Zelazny-style trans-dimensional swashbuckling. The books are inert. It's up to you and your table 'what it's like' so let's all just sail on from the critiques or hot-takes that say D&D 5.5 has a style.
Our group proves this with potency! We're in a hybrid old/new Greyhawk that oscillates between sandbox, railroad, high action, tear-jerking RP, and a dash of Genestealers. Yes, there are Genestealers in our Greyhawk.
6: Eru Tovar
Enough abstracta. Let me extend an open hand, dear reader. mY main D&D 5.5 group is currently in the legendary city of Eru Tovar, northern Greyhawk, Wolf Nomad Nations. They have taken up their BASTION project in the ruins of the besieged and storied town, surrounded by foes who have learned they have the BOOK OF VILE DARKNESS contained in a bag of holding. They are playing 80s modules next to 5.5 DMG encounters and everything in between. One character was bitten by the vampire queen of Tsojcanth. When his friend and fellow was killed last session, he had not yet turned.
Our session 61 tagline: Eru Tovar has two fresh graves... one of them empty.
Go play some bone crunching D&D. Just let me enjoy my 5.5, cu I'm lovin' it.
-B