When it comes to wall paint, there's one cardinal rule: Do not go with the cheapest brand you can find. I made that mistake when I first started painting walls. And the cheap latex garbage I used peeled off in sheets over the next six months. In fact, it became my kids' hobby: peeling off pieces of paint.
What to look for when painting walls
Before you start thinking about painting for walls, make sure you've prepped them properly. Even the best paint looks terrible if you cake it on over blemishes, holes, and dirt. Take the time to clean the walls and patch any rough spots, then give it twenty-four hours to dry.
During those twenty-four hours work on buying wall paints! You want the very best quality, the most expensive brands (like Benjamin Moore and Muralo, both highly respected paints). If you want to go a little bit less expensive but still retain good quality, though, there are a number of excellent brands for painting walls, including:
Valspar American Tradition
This is excellent wall paint, mildew resistant, thick and smooth, with lots of color choices. And it's quite a bit less expensive than its designer counterparts.
Dutch Boy is even less expensive than American Tradition. It does tend to fade a bit more over time, but it's still an excellent product: it gives very smooth, solid coverage and holds up well to the trials of time.
Behr Premium Plus
Behr is a win-lose situation: it is quite prone to fading, so it's definitely not the best bet for your sun room. When it comes to interior rooms, though, Behr is known as a strong, solid paint that resists staining and offers bright, cheery colors.
Your choice of wall paint depends on the room you're painting and the quality you want, but these choices should give you a good shopping head start.