After booting up my game for the first time in ages (and having to reinstall on a new comp), I've remembered that I have no skill in building houses and would rather just gather up the many many others already. Is there an easier way to install lots, or is it still 'load up the launcher and pray that things don't break' method? I also feel that this will end badly if I go on a downloading spree, and the last thing I need is to re-accumulate all the broken and unneeded CC.

The best way to install lots is manually, by converting Sims3Pack to package with Delphy's S3PMPE. Once converted, cut and paste the lot in My Documents\Electronic Arts\The Sims 3\Library (only the lot, other files that could be extracted as well are either content you don't want or content you should put in your Mods Folder). This way helps you to avoid using the cumbersome launcher and installing unwanted CC.

When my sim goes to different worlds, I just go into edit town and copy off a few lots I like. You have to evict the family if they're living there, but you can put them back when you're done; like the MacDuff family in Moonlight falls - few houses have well done basements, and I wanted it, so out you go!

Once saved you can either add the houses in new games via in edit town, or add them in Edit in Game mode in CAW when editing a world. One world I really like has really nice looking houses that render horribly and are unplayable; so I've been replacing them with good, playable EA houses. yes, even some EA houses suck and aren't very playable.

My own houses are ugly but very playable. With these pretty houses I get tired of having my sims go to the garage when my sim casts a curse on one of his roommates in university, for example. The house is nice, but literally has no room inside for sims to do many interactions like spells or get a DNA sample.