I'll start here:
"No storyprogression" sounds strange though, does that mean that nothing ever happens and the town will just die out if you play one sim?
No, the whole town doesn't die.
It's just that no one ages at all, no one dies, no one marries, no new babies are born. The only way a sim outside of the active family can die is if you create the circumstances for them to die through your control of the active family, i.e. you invite them over and they get eaten by your cowplant, or you remove the ladders from the pool and they drown, etc. If John & Jane have a baby, Joe, and Joe grows up and has his own kids, his kids will be friends with the same children he knew as a child. It sounds boring, but it has an upside. You can change active families and play someone else and John, Jane and Joe don't age. You can always go back and pick up where you left off.
It's hard to describe the whole game otherwise, but some major points:
- Sims don't have traits; instead they have five axes for personality. A sim can have 0-10 points for neatness, niceness, extroversion, etc.
- Instead of a lifetime wish, sims have an aspiration. They roll wishes like they do in TS3, but what those wishes are is largely determined by their aspiration.
- The neighborhood is not seamless. All jobs are rabbitholes unless you own your own business (Open For Business EP). To go to your neighbor's house, your sim travels to the edge of their property, a loading screen comes up and your sim and whoever goes with them are magically transported to their destination. You
do get neighbors that walk by and stop in to chat, to a much larger extent than in TS3.
- The sims are much worse at caring for themselves. Expect many hilarious and tragic deaths. This is what made the asylum challenge so much fun in TS2.
- An important component of job advancement is friendship, which functions somewhat differently. A contact never goes away once made, relationships are (I think) easier to establish and not so difficult to maintain.
- Although I have hardly explored all of it, TS2 is just way less complex than TS3. There are secrets to be discovered, but it's just a simpler game.
If I had to choose for you, I'd get it! It's a different experience, but I think it's great. When I played on a laptop which wouldn't support all the EPs (though I have them all), I had to be picky and I'd use the base game, Night Life, Seasons and Free Time. My next choice would be University.
If I might make a suggestion, I'm sure you could find a copy of the base game rather cheaply at this point. Why not just try that first and see if the playing style suits you? The base game is a little on the boring side for me, but in it you'll see all the differences from Sims 3.