I recently got Sims Pets and Ambitions but was getting a little bored. I also recently discovered Story Progression mods which I'm seeing/hearing mixed reviews from. I don't want to get a mod if it's going to slow down/crash/mess up my game but I am definitely interested in trying something new to improve the Sims for me. So with that being said, is a story progression mod (such as Twallan's) worth it?
You don't have to use a mod. A mod isn't something you're required to use. It's extra. That being said, there is a lot of misinformation about game modifications (all types, including CC). I've used mods since Sims 2 and I've never (knock on wood) had a problem with any of them. In my Sims 3 folder, my hacks and package files amount to hundreds of GB to give you an idea. It's all about reading and knowing what you're doing. If you update your mods and make sure you don't have any that conflict and none are corrupted (use Dashboard), you'll be fine.
I read an old post on this thread that said script mods would cause your graphics card to burn. I almost choked myself laughing. This is an example of the thinking people had back in the Middle Ages (taking a bath will cause you to die, anyone?). Nope. Your graphics card will burn to a crisp on an un-modded Sims 3 game (if your graphics card is gaming decent/top-of-the-line) and you use AMD video cards. You have to mod the game just to play it. I think before people try to dissuade others against using mods, they should, themselves, have experience using them. Until then, you're just speculating and causing undue panic. I've been playing the Sims since 2000 and have had un-modded and modded games. I prefer the later.
Also, who says you mod to make the game easier? There are many, many mods out there that can/will make the game even more challenging. Mods that make bills higher, skill challenges harder, etc. Again, you can't assume unless you've actually looked. Besides, EA (silently) backs modders. There are more SimGurus on modding sites than you'd think. They've also had a history of inviting modders/cc makers to special events. It's all about research and with Google, its free
And to finally answer your question, I use Twallan's SP. I wouldn't play this game without it. It does all the things EA's SP purports to do but doesn't. Your townie families will have longevity and they won't all become supernaturals if you don't want them to. They also don't move away before you want them to. They progress and get jobs and have families. And you can play many generations (if you use his additional modules) without your game blowing up on you. In one of my files, I'm at generation 20 and still going.