Mass Effect 2 DLC

The extent of the DLC is very much the same as Zaeed. You get a loyalty mission and you can get comments from her in her quarters between the other missions that you do. Her premier talent is a form of tactical cloak which can be quite fun to use in combat. You also get a cute little side quest involving her in ME3 and she adds some crazy antics into the Citadel Party (similar in extent again to Zaeed's quest and party participation). For me, I like her loyalty mission in ME2 and I do use her as a squad mate on some missions in ME2... so I consider the DLC to be worth it.

If you enjoy James Bond you'll love her loyalty mission. She's friendly enough, and quite a useful squad mate. I recommend you get it.

Buy it.  First, it gives you better non-Cerberus casual clothes than what you can have from the start.  Second, Kasumi impacts a side mission in ME3.  Her impact is significant.  Otherwise, I do like her, but she's a bit consumed by memories.

the DLC is quite fun roleplaying as James Bond/Detective a bit before things explode, it's Shepard after all

2 things I like most from the DLC is the new suit outfit (no Cerberus logo) and especially awesome SMG Weapon "Locust"

This is my DLC ranking for ME2
1) Arrival (kinda essential to the story between ME2 and ME3)
2) Lair of the Shadow Broker (lore, awesome mission and boss, quality, diverse and long DLC, my favorite ME2 DLC by far, despite not really liking the Asari squadmate)
3) Overlord
4) Kasumi
5) Zaeed
6) Firewalker