Pros
Decent benefits agreement. Good amount of holiday entitlement. Union agreement means better job security - VERY hard to get sacked. If you land in a good store it's an easy clock in clock out job. In some stores it's easy to pick up extra hours for your contract.
Cons
Staff aren't valued for more difficult roles. Management are usually poorly trained or have poor attitudes and pass a lot of their workload onto the base rate workers. Company is on a trend of cutting most employee benefits and replacing them with lip service. While some of the benefits are good a lot of them are difficult to access - particularly anything relating to another business Tesco owns eg vision express or pizza express. Replacing most of their staff with self service, then blaming staff for higher rates of theft. No protection / security if your store is deemed to be low risk. High rates of customer abuse. Extra hours are entirely dependent on how your store manages theirs - tends to be no overtime in the new year. Extra contracted hours only appear if somebody leaves, and will usually go to the staff most liked by managers. Lots of poorly trained managers with no knowledge of company policies. Hard to get rid of a bad manager / bad colleagues because it's difficult to get sacked for anything but cut and dry gross misconduct. Entirely variable based on the store you're in and who you work with. Wouldn't recommend working in an express to my worst enemy.