This is going to be a bit stream-of-consciousness. If I try to edit or organize too much, I end up not getting anywhere because there's just too much for me to talk about. I've been waiting a decade for this game, and now that it's here I'm pretty much gushing.
Starcraft is one of my top 3 all-time favorite games. I could not get enough of that game back in the early 2000s.
I've had a few days in Starcraft 2 beta, and so far it is more an SC1 redesign with pretty graphics than a different game. And I'm perfectly happy with that.
Right now the beta is multiplayer-only, with 1v1, 2v2, and ffa available on a pool of about 5 maps. So it can get a little repetitive, but it does allow Blizz to focus-test balance. I've played all of the races a bit, and after specializing in Protoss for about 50 games, I've switched over to Terran. I never liked Terran back in SC1, partly because I disliked siege tanks and the race's comparative lack of mobility. The race has been vastly improved by mixing up the roles of some of the basic units, improving their air options, adding a heavy high-tier ground unit, and reducing their reliance on siege tanks. They have a new heavy infantry unit, called a Marauder, that, unlike the marine, can take a few hits, and is strong against armored enemies. You can make a reasonably durable ground force early on now, which makes Terran a lot more attractive to me. Conversely, the Protoss ranged units that replaced Dragoons can't take much punishment and rely in maneuverability and spell casting.
OK, I'm getting too specific now.
There is so much I could write about SC2, but I'll try to limit myself to a general overview here.
The visuals are great. They have the "Blizzard touch" in the art direction, and the effects are well-done. If you zoom in close the models look blocky, but they look perfect from the normal distance. Most have a unique profile that makes it easy to keep track of things at a glance and avoid losing your units. The animations blew me away, especially for the construction of the terran and zerg buildings, and the transformers-like animations of the Valkyrie and Thor.
Likewise, the music is excellent, though a bit limited right now. Playing the same race, I hear the same tune far too often. The sounds are what I expected: they hearken back to the SC1 sound effects, but are much higher quality.
Korea is probably going to be pretty happy, because this game is Starcraft 1 only prettier. Most of the iconic units are still there, except - notably - the Dragoon, which has been replaced by two similar units, so its absence is less felt.
It's also balanced better overall (not that SC1 wasn't well-balanced, just in a different way), with a larger variety of useful units and counters. There are some units that got very limited use in SC1, but in SC2 so far I've had a good reason to bring out every single unit at some point or another.
Games tend to last 10-15 minutes, except for the occassional knock-down-drag-out 45-minute slugfest. I've also had some epic matches where my force reaches the enemy base just as his force reached mine, but instead of either of us retreating to defend, we both just race to burn the bases down more quickly while expanding in hopes of buying ourselves a few more minutes. In these cases, Protoss generally wins because of Observers, cannons, and some unit balances (such as the fact that Carriers can kite Battlecruisers).
The current playerbase seems . . . more skilled than I expected. I'm a reasonably good player, and was originally placed in one of the top leagues. I decided to screw around and play random races for a while, and that got me knocked down a few leagues. Even in the below-average league that I'm now climbing out of as Terran, I'm encountering so many people who know so much about the game even though they are supposedly below-average players. The pool of people in the beta must be dominated by pros and superfans. There are only about 5k people playing at once and I think roughly 10-20k in the beta at all, so hopefully the skill levels will spread out a bit when the game releases or more beta opt-ins go out. I'm shocked by how few people I encounter who don't know what they are doing. Everyone seems to at least know the basics, and about 70% seem to know macro tricks like kiting and running, and seem to know unit counters much better than I expect. I thought I'd be ahead of the curve, and instead I seem to be right in the center.
So far, Starcraft 2 definitely embodies the idea of "just one more match". I can't seem to stop!