Agreed - only do renos if there is a reason. Also, consider the neighborhood and overall house price range when adding upgrades - I've heard that a lot of granite-countertop-type upgrades don't even add enough value to recoup the money of the counter/etc! For example, while I would never do any crazy countertops, we recently got a new furnace (installed by friends!) and we saved so much on labor, I sprung for the new AC at the same time. The house already had AC and our neighborhood is full of the kinds of people that leave their AC on when it's 75 out. I figured it would also be nice for those very few 90-degree days we get so that we don't have to hide in the basement, but we made it through this summer without using it at all (old one leaked condensation on the basement floor)
We've been in our house for about one and a half years and most of what I've done was painting. When we moved in, everything was super 80's style- the old people that lived there are exactly as you described. They moved in in 87 and probably never did much updating, but the house was very well maintained and had awesome things like blown-in insulation and new windows. I'm so glad I've gotten most of the wallpaper borders, way-too-much-yellow, and trim-painted-the-same-as-the-walls stuff gone!! I also switched out a lot of the light fixtures to a more modern brushed-nickel or similar finish, the ones that were here were all brassy and old looking :\ If you're lucky you can find light fixtures for $20-$50 each and they're very easy to switch out.
As far as things I want to fix up in the future, most do involve the kitchen and bathrooms but they all have reasons: the kitchen is small, but then the actual kitchen part is crammed into 1/2 the room so that there's space for an "eat in" kitchen... with a dining room right next to it. I want to redo the kitchen to kill the eat-in area and make it nice and roomy. I like cooking so I would like it personally but hopefully it would add a lot of value. One bathroom has a dumb corner toilet and it sucks, so I want to get rid of that, and the main bathroom doesn't need a *whole* redo but it could use a vanity with more storage (and there's room in the bathroom for a bigger one). Also, our basement needs to be refinished, a lot of it (carpet, paneling) got destroyed in the "october storm" of 2006.
I think I should also add that I love doing these things. I get a lot of satisfaction from finishing a project and knowing that *I* did it. I dream of retiring before we're 100% ready and getting some rental properties in our hometown (a college town, lots of renting opportunities), so this is also kind-of practice for that.