I've had the game for about 12 hours now and I can honestly say it's great. If you watched the live stream videos at all, they are spot on in terms of gameplay.
I feel like I've barely scratched the surface of manipulating emotions and all the unique interactions. I've got a male and a female living together as roommates and focusing on their careers at the moment (Astronaut and Artist, both are great!) but I've been trying to get them to like each other more with limited success. I feel like I need to make that Flirty room one of the live streams referenced and stuff them in there for an evening.
The loading times are minimal, the game runs like butter, even on low graphic settings from what I've read of others. The collecting is tons of fun too. I have barely even looked at Build Mode yet, I just dove right into playing the game. The UI is streamlined and intuitive and the graphics are awesome!
My best advice: upgrade from the cheapest appliances & comfort furniture right away. The cheapest stuff gives you Uncomfortable Moodlets. You'll have enough Simoleans to upgrade the basics with some left over. My first week of bills was only $530 and I was expecting a lot more from what the SimGurus said in the last week, but my home is a little basic with average items in it for the most part.
Next best advice: You have a daily task every day to complete for your job. This is different than the tasks listed underneath your Performance Bar. If you hover over your Performance Bar, you will see your daily task. Don't forget it, it gives you a good boost for your performance and if you forget about it too much, you won't advance as quickly as you could.
Have Fun! I'll check back into the forums and answer as many questions as I can for the next few hours. Drinking coffee now to stay awake