heists:
kinda bad, you mostly likely will do them only for achievements and then never touch them in your life ever again.
also, all heists except the train ones (by the way, train originally required you to find military blueprints in one of trucks to even be able to access it) are a reference to movie "The Heat"
"Gage" and his name might also be a reference to "The Heat" and "Gage Armored Express"
weapons:
Commando 553 - The meta of 2014 that became a part of 50-54 damage rifles during rebalance. originally used to be the better version of AK rifle, as well as alternative to good old CAR-4. can reach fairly good concealment.
Gruber - it's okay, i guess? pretty much a great stealth weapon that nowadays gets mostly used in loud builds due to it's ability to reach 34 concealment.
Swedish K - it's alright for the price. can reach like 32 or 33 concealment, and can be used as an anti-dozer weapon due to rebalance moving it to "High-damage SMGs" class.
They're okay. most of them have their counterparts that do the job better, but most of these weapons still can hold up well even on Death Sentence due to their high concealment, which allows you to benefit from sneaky bastard/low blow while using them. gruber with that one LMG can also reach 4 detection risk, by the way. they also can be used at level 0, so if you prefer becoming infamous with reputation you might find them being useful.
masks and materials, patterns, and all that stuff - never used them. but hell, i LOVE hockey heat mask.
weapon mods:
see more sight - one of the best sights in this game.
soundtrack:
hits hard.
def WOULD recommend buying this DLC. and not only for a see more sight, but also for it's weapons that are good if you're playing on older versions of payday 2 or prefer becoming infamous with reputation.