The film looks much better in widescreen than in the older full screen prints. This helps.
The IMDb user reviews are good in pinpointing the film's attractions and lacunae.
Taking the film for what it is, with a lot left out, it's not bad but also not fully satisfying. It's very clear that the rise and fall are treated too sketchily. The film's strong point is in creating just about the right tone for such a film, one that doesn't glamorize, one that doesn't absolve the gangsters or reduce their motivations to shallow psychological ruminations. One comes away feeling that one understands the Kray family reasonably well. It's no lengthy Godfather epic, however, which is what some fans of the Krays wanted.
Classic gangster noirs like White Heat, The Gangster, Baby Face Nelson, and also The Brothers Rico and New York Confidential, deliver a far different feeling than a movie like The Krays. Carlito's Way and Scarface are much more clearly noir. I don't think the makers of The Krays intended to make a noir and what resemblance it has, which is some, is therefore not that strong. The element of staging to create conflict and psychological entrapment or instability is missing. Too much time on peripheral family doings undermines the required feeling of tragedy.