I've heard a lot about people using this program to package their houses/lots for upload here on this site because it allows the lot to be compatible with all expansion packs. Is this true? How exactly is it better than using the in-game packager? Also, how exactly do I go about doing this..

No, it's not true that it makes it compatible with all eps, it just enables you to strip out custom content that you don't want included with the finished lot, - like every recolor for an item when you really want only the one recolor, you can take out the unneeded recolors...

I'm pretty sure there is a tutorial about how to use it somewhere around where ya can download it from... sorry I don't have a link handy...

Here is the link to the S2PCI instruction manual.

http://sims2pack.modthesims2.com/index.php?page=4

However this manual is not quite clear enough as to figure out how to upload lots with this program. If anyone out there knows of any other websites explaining this process or anyone willing to share information on the process that would be awesome. Thanks!

Please read http://www.modthesims2.com/showthread.php?t=124539 as part of the MTS2 Creator Guidelines forum.

It explains how to package and prepare a lot for uploading... as the title says.

May I suggest reading through the Creator Guidelines section if you have questions like these?

Thank you