I just finished up a replay of this game yesterday. Initially I was going to go the Renegade choice route, but the first time I played through on Paragon, I didn't quite get the ending I wanted. Nobody on my team died, but I lost the crew. So I decided to restart with my same character, getting a nice money and resource boost, bought Project Overlord and Lair Of The Shadowbroker, and played the whole thing again. With all the DLC included, it raised my total play time to 36 hours and 36 minutes.
This time around, having Kasumi from the beginning made that DLC purchase actually feel like it was worth it. Her mission sucks, but I like her abilities and some of the stuff she says throughout the game. Meanwhile, Zaeed once again mostly sat unused. At one of the points where two character argue and you have to take sides, my Paragon level wasn't high enough, so I lost that character's loyalty. I didn't have a backup save (everything was perfect up until this point, lol) and was freaking out that I'd have to start all over again. Then when I got my Paragon level up I got the loyalty back. Whew!

Anyway, I saved most of the extra missions and planet-scanning stuff for after I finished the game. Did Project Overlord while going through each galaxy, and enjoyed that DLC. I did miss the scanning achievement though...forgot all about scanning with the Firewalker vehicle, since I did that DLC mission after Overlord. D'oh!

I enjoyed Overlord's creepy feel in some of the bases, and loved the presentation at the end. It was fun.
Lair Of The Shadowbroker was last, and yes, it really should have been a part of the game from the start. One of my complaints about Mass Effect 2 was that they kind of brushed Liara and the whole Shadowbroker thing aside, and this definitely addresses all that! Not gonna spoil anything, but the ending may have some people hating Bioware's storyline choice. You also get another ship's quarters-style area you can revisit.
spoiler (click to show/hide)
Here you can help broker some deals and purchase guides to the richest planet resources, plus read dossiers and a lot of the main cast, checking into their personal lives. There's some pretty funny stuff in there. You can also watch some very brief (new) video clips. It keeps saying to come back to see more, too.
And yeah, you can re-romance Liara if you want to, too. Like the Kasumi DLC, this one definitely "fits" into an earlier part of the story. It doesn't feel like an epilogue (not that they said it would be), and I get the reason why it's not, but I would like to a DLC pack that does that.
So now I'm done with the game again; back to Metroid Other M and time to start up Halo Reach. Maybe one day I will replay it on an insanity run as a Renegade Shepard. Wanted to be the male version, but the female version's voice actor just fits better, IMO. Actually what I really wanted to do was play through the original game again as "Asshole Shepard," but it seems so hard to go back to ME1...