My opinion about the shifts:
Heliolisk moved from RU to NU - RIP Feraligatr, nice electric type, can break apart Mega Steelix and can screw up most water types in the tier.
Quagsire moved from RU to NU - RIP Feraligatr 2, I actually expected this dropping, it's nice for stall, and pretty nice balanced wall for who wants to stop sweepers.
Virizion moved from RU to NU - I think it has the potential to get suspected, it has decent attacking stats, amazing speed and access to boosting moves like Swords Dance and Calm mind, with offensive moves like Giga Drain, Leaf and Close Combat as well as coverage with Hidden Power Fire and Stone Edge.
Claydol moved from RU to NU - Welcome home :] and yeah, ask Hitmonchan to give us a visit in May!
Mawile moved from RU to NU - Mawile's thoughest challenge, will it be strong enough for NU? Or will it's journey end in PU? It has nice moves to abuse Sheer Force and it has a nice typing to abuse Intimidate, although defensively it might be outclassed by Granbull.
Accelgor moved from NU to RU - Really sad with this moving up, there goes a great spikes stacker, special attacker and check to Malamar, offensive teams will resort probably to Qwilfish to get spikes up.
Glalie moved from NU to RU - Not really caring about this guy, I didn't use it since it was PU and in NU, what could it do that Qwilfish couldn't as suicide lead?
Kabutops moved from NU to RU - Kinda sad for Rain teams, I was making one for the suspect test and had kabutops, dang, but outside of rain I won't see much difference, I always liked using Sandslash more as a spinner.
Also, something cool to know is that out of these 5 things that dropped, 2 of them can Check it can kinda check Mega Steelix, the upcoming suspect: Heliolisk can do a ton for even specially defensive sets with Life Orb/Expert Belt Surf and Focus Blast, having high chances of 2HKOing it, and Grass Knot can also make big damage. Quagsire can burn non-rest sets and Curse Quagsire gives Steelix some headaches. Claydol, Mawile and Virizion can't 2HKO it (Virizion can OHKO defensive sets with Focus Blast, but not sure if it will get much use), but they can all at least 3HKO it, Claydol does 30%-36% on defensive sets, 42%-50% on offensive sets with uninvested Earth Power, Mawile does 27%-32% on defensive sets, 37-44% on offensive sets with neutral natured uninvested Fire Blast, Virizion can do 41%-49% with Close Combat on sets without Defense EVs.
About Feraligatr, well, I think Samurott will start to get way more used in NU replacing Feraligatr thanks to Grass Knot, hitting Quagsire, making it way better against stall than Feraligatr.