More substantial ME2 review:
As you may know, I imported my ME1 savegame into ME2 so I continued my Shepard's (or Shipard, as I pronounce it - his first name is Jean-Luc) saga. This will carry over your appearance, a semblance of your paragon/renegade scores from ME1, some additional things like extra starting credits if your ME1 was rich, and of course all the choices you made in ME1.
Even if you load a character from ME1 you can tweak just about anything about them except for their name, so you're not completely bound to them. What you can't change or choose is what you did in ME1. Similarly, if your character is newly created he or she will just be following the canon storyline.
What kind of decisions carry over? Who of your teammates lived or died in ME1, who you made Councilman (Udina or Anderson), whether you let the Council die or saved them, who your romance was, etc. And a whole host of small choices that don't usually affect the main storyline much but are still very immersive. You really have the idea that what you did in ME1 made a difference.
Now, the game itself. It's not an RPG in the true sense of the word - yes, you have a character, a class, some stats and room for customization, a party and a lot of decisions to do and make. But inventory is all but out - there are a few different armors and a few different weapons of each kind (assault rifles, pistols, shotguns, sniper rifles, SMG's and Big Guns), which you can acquire through the game and switch to your tastes. They do not differ so much in stats as in purpose. For example, of the three assault rifles I had one was a good balance between firepower and accuracy, one was accurate but shot in bursts with limited ammo and one had a shitload of ammo but was a complete spraygun.
Upgrading can be done by finding or buying blueprints and researching them at your ship. These are things like +X % assault rifle damage, or +X% armor penetration or accuracy, +X% biotic squad damage or cooldown, etc etc. As I said, the basic armor types are limited but along the way you will find different helmets, shoulder parts, knee parts and whatnot that will boost seperate stats or abilities. Don't expect too much, however. You will likely only bother with it 5-10 times in a game as it doesn't really matter all that much (stat boosts are minor).
Now that all sounds pretty horrific for an RPG fan like most of us here, but they did us and themselves more of a favor than antyhing else. The inventory aspect of ME1 was incredibly dull and bloated. Either they turned it into something of DA's diversity or shaved it down to what it is now: functional while keeping the RPG barebones. It works.
Now we got that out of the way: just about every issue of ME1 has been tackled and turned around. Combat is smoother, faster and more exciting. Ability is important now as headshots and bodyshots affect enemy behavior and your damage output. You still can't control your squadmates directly, but if you want you can give them more accurate orders...but in general I just let them off the leash and do their thing. Worked pretty well. The random planet side missions are now all unique and no longer involve the horrid Mako driving. They are often pretty generic in the sense that you still need to kill shit, but the settings are WAY different and there are some that are even puzzles rather than anything else. No issue there.
The only tedium in ME2 comes from the planet scanning. Do yourself a favor and get 2 upgrades ASAP: the one that lets you scan faster and the one that gives you 60 instead of 30 probes capacity. Basically you scan planets for resources (irridium, platinum, palladium and element zero), fire a probe if you detect some and mine them. These resources are necessary for upgrading your items, character, abilities and ship. So you WILL need to do some scanning if you don't want the lamest outfitting in the universe. But it's not by any means mandatory to scan everything: I scanned every planet in the game and ended up with 300.000 of every resources except Element Zero (it's rare). The biggest upgrade in the game is 50.000. So you'll be just fine with scanning occasionally. I also refused to scan any planet that had a "moderate" or less rating of resources. Only planets that were "rich" or "good". i advise anyone to do the same.
To the game itself then: it's amazing. The graphics are tight and sometimes inspired (I was in awe several times), your teammates are mostly interesting and some have incredibly dialogue (Thane, the assassin, is a great example) and you'll travel to some wonderful and exotic places. The dialog system was already great and has been further improved with the 'interrupt' option, and, well, everything just feels right. You'll meet old friends from ME1 who will join your or have a new life now, but seeing them again always makes you feel great. When I saw Wrex again, one of my favorite ME1 characters, it was like..."dude!!". Great stuff.
What I should perhaps stress the most is the amazing cinematic direction of the dialogues and cutscenes (all in-game engine of course). It's unsurpassed in gaming, really. It's like you're playing your own sci-fi epos. And then, to top it all off, there's the final mission. People will die. Maybe your lover, maybe your favorite party members, maybe the ones you hate, and maybe...you. You will have to be prepared for the ride and make the right choices. It's one of the most adrenaline-pumping, emotionally challenging finales I've ever played, bar none. I only lost one party member myself, but it could have been worse...a friend of mine lost two, one of which he really liked. The fact that some party members have gone along for two games with you and then might die depending on your actions feels worse than you might think.
I didn't even like ME1 THAT much. But ME2 is one of the most ambitious, epic games (the music, too!!) I've played in ages. It's not the sweeping classic RPG epos that is Dragon Age, but it's a monument in its own right. Nothing but recommendations. The first 20 minutes are already jaw-dropping, and I just gushed over the finale. Also, Joker is actually funny in ME2.
DISCLAIMER: I think all of this is to some extent colored by the fact that I took the same character through both games. It's 'my' story. If you don't have a save of your ME1 character this may not be as wild a ride as when you do. There's a way of fixing some of that though: this website has a collection of ME1 saves with all kinds of characters who made/did all kinds of choices and romances.
http://www.annakie.com/me/
Since you can tweak anything except your first name (and it's never mentioned in the game), you can basically take your pick of the sort of character you had in ME1 and recreate him/her from there. Maybe useful for Satis.