Wow, this is awesome. I have a lot to say about this DLC so sorry if this gets long winded. ( An probably some spoilers, consider yourselves warned. )
Firstly it must be said this DLC is amazing, easily the best DLC so far. You can tell a lot of work was put into this content and it shows, it's also very much appreciated. I dearly hope you will continue to release DLC like this, and I'm making sure to tell all my friends about it so they can get it themselves and hopefully convince you guys to keep making this wonderful content.
The new gameplay elements were very well done. From the car chases to the environmental damage, I'm amazed you managed to do so much without a completely new patch for the game. All of the big boss battles were unique, different, and a hell of a lot of fun.
The best addition, of course, is Liara herself, specifically as a teammate. Even though she is only available for this single DLC it was awesome having her as part of the team once again. Good call on giving her Singularity as a base power, by the way I would have been disappointed in her if she wasn't the awesome biotic she's always been. On that note Stasis is awesome. It makes me want to build an Adept now that there's this cool new ultimate crowd control available. Playing on my Infiltrator I found it very useful when taking out multiple targets. Putting stasis on one allowed me to kill another and be ready to kill again when it wore off. Once again major awesome. If you're still debating adding it to ME3 then put my vote firmly in the YES column.
The other huge thing for me is all the dialog that got added. From the cinematic smart talk / banter of the car chase to the deep relationship conversations ( and yes a huge reward for those who stay loyal to Liara

) there was clearly a lot of dialog put into this DLC to cover all the options. This more than anything else is truly appreciated. It was a huge deal being able to continue Liara's relationship and being able to talk to her about her behavior. I really want to see more of this as much as possible. The lack of dialog particularly amongst crew members new and old has always been an issue of ME2, and it's always nice to see more of it being addressed through DLCs like this.
Really I could go on with the things I liked, but that will just involve pretty much talking about every second of this DLC. I think the top faves above should be helpful. So with that in mind let me mention a few of the things that I didn't like in this DLC, although keep in mind all of these dislikes are pretty tiny compared to all the good things that this came with.
I mentioned above how much I loved the added dialog and character development that you put in here. However I still need to point out this only involved people directly involved in this DLC, in particular Shepard and Liara. Everyone else involved gets nothing. Specifically there is only one line in the entire DLC - at the bombing - spoken by any of your other squadmates and even that was probably just reused audio. I had Garrus and Tali with me ( who lets face it, HAD to come along for this one ) and I wanted them to say something about this whole ordeal with their former crewmate. Instead they remained completely silent yet again.
That said I understand all too well the limitations of the development cycle. So while there was not as much actual dialog as I would have wanted the fact that so many great character insights were provided in the dossiers and the videos in the Broker's base was a great and very welcome treat. I still would have preferred learning all this from actual conversation options with the crew, but as consolation prize of sorts it is very much appreciated.
One detail that kept bugging me and probably could have been addressed was the constant assumption that Shepard was fully working with Cerberus. A lot of people blew up the base rather then continue working with them, a lot of people don't like the idea that we're still forcibly tied to this organization. I was given the impression that once you tell the Illusive Man off you're no longer working with Cerberus anymore. But once again Cerberus are the ones that give you the Shadow Broker intel, and throughout the game your ties with Cerberus are brought up over and over again. The Spectre Vasir says as much quite bluntly and never once can you say you've cut ties to the organization, that's one option that most definitely should have been included in my mind.
Are we going to be stuck with Cerberus from now on? What about ME3? This is going to get extremely frustrating if we never get the choice in this matter. Considering how important your choices are in this game, this is quite a letdown.
Lastly one issue I ran into is with the hostage negotiation scene with Vasir. There are renegade and paragon options to resolve the situation but I was never allowed either option. My renegade bar was maxed out by this point but still I wasn't able to pick anything. Requiring a high renegade or paragon choice is one thing, but this just seems way too high if you need a paragon/renegade score that is literally off the charts to pick either one. Granted the renegade option to shoot Vasir through the hostage was pretty badass, but still it's annoying that I didn't get the option when I feel I should have.
Well that's all I need to say for now. I could go on gushing about this awesome DLC, but you guys get the idea. Keep up the great work. I really look forward to whatever you come up with next!