Looking at the reviews it seems that, while not everybody likes it, the vast majority score it highly.
For example, of the 9760 reviews on TripAdvisor, 78% score it as 'excellent' or 'very good':
https://www.tripadvisor.co.uk/ShowUserReviews-g186338-d1421189-r323937336-London_Steakhouse_Co-London_England.html
There are 846 reviews on Bookatable, with 90% of reviewers recommending the restaurant:
https://www.bookatable.co.uk/marco-pierre-white-steak-alehouse-bishopsgate-liverpool-street-london
Opentable has 2403 reviews, with 79% fitting into the "I'd recommend it to a friend" category:
https://www.opentable.co.uk/marco-pierre-white-london-steakhouse-company-city#reviews
On Virgin Experience's own website there are 345 reviews, with 86% of them awarding either 4 or 5 stars:
https://www.virginexperiencedays.co.uk/three-course-dining-experience-and-cocktail-for-two-at-marco-pierre-whites-london-steakhouse-co-sp1
So you've got over 13,000 reviews to guide you but opinions about restaurants always seem to vary widely. (A friend took me to an Indian restaurant which has amazing reviews on TripAdvisor but we were both very disappointed by it).
Hopefully you'll concur with the majority and enjoy your experience. Bon appetit!
(PS: If you're trying to find it, note that it's not actually on Bishopsgate. It's just off it, on Middlesex Street).