I expect it to be fully playable. There haven't been many total game breaking bugs in past games and even those took a few days for people to start stumbling upon.
As with most games.. you can pretty much guarantee a freeze or a crash if you play the thing for any lengthy period of time. Best way to avoid frustration with crashes is to keep plenty of permanent and rotating saves. I just get into a habit of saving. I'm sure they'll have some sort of rotating autosave feature like skyrim did. (that saved my ass a few times.) Hopefully they'll have even worked in a quick save for consoles.
Bigger bugs in past games have usually occurred during heavily scripted events such as story missions or side missions..and for the most part.. not until later into the game. My play style seems to work well with avoiding these bugs as I tend to stay away of story in favor of exploration. By the time I get to where the bug was, it's been fixed. It also helps to come to the forums every day and read bug reports.. if people start claiming something is messing up their game, just avoid that and do other things in the game until that thing gets fixed.
The only bugs I remember in skyrim were 1. crashes, 2. couldn't get a woman to leave a cave without shouting her out of the cave, 3. a broken quest pointer for the bards college that wouldn't go away and 4. some random quests stuck in the log even though they had been completed. .. All in all, pretty minor stuffs for such a big game.