Gotta feel for this due to the later emergence of 'The Shawshank Redemption' and even 'Prison Break', but 'Escape From Alcatraz' still merits its own props as a great film.
I love a good prison escape flick, shown by my love for those two aforementioned productions which do improve on the formula; TSR - one of my favourite films, fwiw - particularly must've took a lot of inspiration from this, I noted a fair few similarities.
With the cast, you have an excellent performance from Clint Eastwood. Patrick McGoohan fits his role nicely, while Paul Benjamin and Larry Hankin are the best of the rest. I would've liked more development for the characters of Fred Ward and Jack Thibeau, who felt a little tacked on. Elsewhere, Danny Glover makes his acting debut in a tiny, tiny role.
I found the pacing to be very good, sure the story I guess is obvious in terms of its direction but I still got tense and edgy whilst watching the escape take place. The ambience of the film is a positive too, with the exception of one moment early on where there's an overly on the nose lightning strike as one of the characters mentions Alcatraz - nothing major, it's a nit-pick and it's my only one so that's a big plus.
Interesting to note this was the final collaboration between Eastwood and director Don Siegel, take out 'Coogan's Bluff' and that was an extremely effective partnership - this 1979 release and 'Two Mules for Sister Sara' being my favourites.