I've been CPing Umbra every chance I get. The BG is no worse than certain sections of Lylat Cruise imo (stage rumbling and turning red when entering Corneria's atmosphere) and the rumbling while admitted obnoxious serves the function of telling you when platforms are coming or going. But other than that, I really love this stage. It's kinda like a more balanced Pokemon Stadium 1. Being the only high ceiling stage other than BF is very nice for variety as well.
Referring to
this thread's labeling of platform arrangements, Meta Knight has nothing that comes close to his circle-camping capabilities on Duck Hunt on any of Umbra's arrangements but
arrangement #6. On #6 he can stall for time by circle camping the main & bottom platform in both clockwise and counterclockwise motions. Most characters can do this actually. However, being caught on the right side of the bottom platform when it starts to go away puts whoever was on it into an edge-guard situation, where they risk getting stage spiked if they try to jump directly to the ledge or just knocked into the blast-zone if they try to use the right-hand platform to recover so there is risk involved.
Something to note before going forward is that each platform arrangement is "active" for about 20 seconds with the one exception of #7. However, platforms may linger longer than 20 seconds due to them all having different ending animations. During their ending animations, arrangements stay on-screen for an additional 5-10 seconds while moving away from the stage until they're completely gone.
Arrangement #7 is active for probably the least amount of time of any arrangement (about 16 seconds total with no ending animation at all) and would only be an issue if it lasted longer. The camera also doesn't zoom out to show when the platform is moving in so it's very likely that by the time players even see the platform, it's already been out for 1/3rd of it's total duration. And once it's moved back off-stage, much like arrangement #6, it forces whoever was on it into an edge-guard or juggle situation. I consider this transformation like an
extremely toned-down version of the PS1 windmill. You can launch people into it and hope they don't tech but if someone tries camping the top of the platform like Cloud charging limit, just wait underneath them and juggle them when the platform goes away.
Arrangement #3 has some potential to be abused for some pseudo-planking. Some characters can grab ledge, let go, Up-Air, land on the platform, then either wait on the platform or eventually Up-B to snap to ledge again. Naturally this benefits characters with invincible Up-B's like Mario's & Marth's more than it does anyone else since any advance to land on the platform to stop them from stalling is met with an invincible anti-air to ledge-snap. Any other characters that try this risk being edge-guarded or even spiked.
I don't think that comparing this stage to Delfino is even remotely accurate. The stage is far more akin to Smashville, T&C, Duck Hunt, and Pokemon Stadium 1 from past games. A 20-second-long walk-off that will only ever appear once (read: one time per game) in 2-stock format due to the 6-minute timer (7 transitions, 25 second each, and 25-30 seconds of downtime before each new transition) is not enough to make that comparison. Delfino upsets stage control constantly, Umbra always has the base FD platform much like T&C. There are many, many reasons that Delfino is a bad stage and Umbra really does not fall under any other them.
This argument dates way back to early Brawl but to this day, the Smashville platform is one of the most abuse-able, MU-changing, unbalanced stage platforms in the Smash
series BUT we're used to it. And let me tell you, we'll get used to Umbra Clock Tower too. 3/7 of the platform arrangements are just the standard semi-solid platform above the stage, another one is literally Yoshi's Island Brawl's platform layout, every platform layouts is on a 20-25 second timer, never show up again in the current match, no water, no stage hazards, same blastzones as BF, and the stage becomes FD for a full 30 seconds immediately after every single transformation. Everything that is abuse-able about this stage has clear downsides to doing it unlike say camping the Smashville platform or circle-camping Duck Hunt's Tree & Bush as Meta Knight. All that said, I think Umbra is a CP stage very comparable to Duck Hunt, better in some ways actually but worse in others.