I've been playing all week, and have done all but the last boss phase of the raid (LL370+ DPS gate, I think) and I'm really liking it. No expansion will ever top TTK, but ROI is a nice attempt.
The story stuff is short but well done. The exotic weapon quests are especially good for nostalgia and lore types.
The new strikes are good. I LOVE the Archon Machine Priest one, particularly for the boss.
The new Crucible mode (solo and team Supremacy/Kill Confirmed) is hectic and a welcome addition because it really ratchets up the pace. Especially on The Drifter where the lack of gravity causes dropped crests to float!
The raid felt really great. Less frustrating and time consuming platforming this time around, which was much appreciated after running King's Fall so much the past two weeks for Y2 Moments of Triumph. Bosses require lots of coordinating movement amongst the entire group. Early to call it but it might be my favourite raid so far.
There are a bunch of system tweaks that improve leveling reputations now, mainly the fact that you can choose weapon or armour rewards now. You'll still be boned for artifacts and ghosts past 350 since they don't drop frequently.
My real negatives from ROI come from things like leveling now feels like such a slog past 350 (remember how I said the raid's final boss I'd basically a hard DPS check, requiring LL370+?) because you need drops. People have resorted to exploits where they can farm Omnigul to drop the 2-3 blues per kill in order to level since doing this playing strikes regularly (or playing for single legendary drops or exotic engrams with Three of Coins in crucible haha) takes a long time.
Archon's Forge also seems like a bungled opportunity compared to Court of Oryx. You can only carry one SIVA Offering (starts AF fights, similar to Runes in COO) and rewards of any kind are not guaranteed. So not only are you rarely getting the means to play in AF, it's a gamble if you're relying on it for any kind of reward other than progress toward a bounty or something like that. I still need to spend more time with it to get a better handle on it, however.
I really do think ROI is a great expansion but it has its drawbacks that might slow people from properly enjoying the raid until they can get above 370. The game is great fun when you're under 350 since it's easy to level and enjoy the new content, but when you need to go above 350 for more challenging stuff (NF, raid), trying to get there can be a slow grind.