So I saw this last night, having booked the ticket ages ago long before there were any reviews or offers
It was as terrible as I'd read, but sadly not "so bad it's good" terrible, it really is just terrible.
Sheridan and a couple of the other actors are good, but they've just got such a hopeless book and staging. The much touted outside bit where it's said that she crawls through the streets of soho was a nonsense, she literally walks (not crawls) about four haphazard steps across the narrow road at the stage door round the back of the theatre and straight back onto the stage, nowhere near what they did in Sunset Blvd.
I suddenly remembered about half way through act 2 that her co-star in the "play within a play" that she's doing is her ex lover, and then all of a sudden some (but not all) of what I'd seen made sense, they had said that he was her ex at the start (I've never seen the film) but it was so poorly written and so all over the place that I'd forgotten this crucial detail. So if you go to see it (only if there's very very cheap tickets around) do remember that important plot point.
There's continuous overuse of a massive centre-stage video screen, there's probably two scenes where it was useful, the rest of the time it could have done with being flown out. One particular scene they put live headshots of various other actors' "reactions" up on it full-screen, including some of the stage crew, and you're just sat there wondering who they're supposed to be, it was like how by about episode 6 of The Apprentice there'll be a couple of randoms pop up who've been there all along but done nothing, so you don't know who they are or anything about them.
Weirdly, there's a scene in Sheridan's' apartment with a sofa and shes puts a big handbag down next to it. When the crew picked up the sofa to take it off stage her handbag fell over and an actual foil-wrapped creme egg fell out and rolled under where the sofa had been, so the crew removing the sofa didn't see it. And it then sat on full view in the middle of the stage floor for the whole of the next scene until one of the actors diverted his exit to pick it up and put it in his pocket. Was it a secret snack for Sheridan? Is it her actual handbag? crew playing a trick on her? a weird "easter egg" in-joke that I didn't get? (I mean the play is set on Broadway, where they don't have creme eggs). Pondering why there was a creme egg in the middle of the stage was one of the highlights of the performance.