I say go for it. That said, I have seen many bad paint jobs. It's something that many people think they can do as it looks easy but you can easily make a mess of things. I own several rental properties and I can repaint a 1200 sqft house in a weekend. A few tips to get a better quality end product:
Cut in with a brush first and then roll out. Brushes will leave streaks and the roller helps roll those out. Cut in is where you use a paint brush to paint the inside corners and near trim that a roller can't reach.
NEVER. And I really do mean NEVER use your wrist. Your wrists are most likely too weak to do a good job, you will flop paint all over. Instead lock your wrist & elbow and use your stronger shoulder muscles. Or even better, lock your wrist, elbow and shoulder and use trunk rotation to move the brush. You will be able paint much straighter lines doing this. Combined with the other tips, I don't use tape anymore so that saves me a bunch of time and expense.
Less is more when it comes to paint. Don't dip the entirety of the bristles into the paint. Dip maybe a half inch. A little more if you're doing a bigger area and less, even just barely touching the paint, if you have smaller areas. Sometimes I will use the brush in the middle of the wall to help remove excess paint that has accumulated.
A 2 1/2" angled brush is my favorite brush to use.
When cutting in, after you dip your brush, start away from the corner/trim to get the excess paint off and then approach the corner/trim. Even if you barely dip your brush, there will be excess paint on the brush that can pool up and get on the ceiling, trim or somewhere you don't want it. I like to start about 2"-3" away from the corner/trim, brush in both directions to remove excess paint, and then work my way into the corner. You can then go back to that starting point to soak up the extra paint. Re-dip your brush when the paint runs out and repeat.
When your brush comes in contact with the surface, the bristles move. That sounds like, "Well, duh!" but you need to remember that. Make contact with your brush and then move it into position when cutting in. Once the brush has fanned out, move so just the tips of the closet bristles make contact with your edge. You only need paint from the outside of the brush, not the middle, to be at the edge. Many paint mistakes happen, especially where trim meets wall, when bristles flare out unexpectedly and touch something you don't want. Find the flare, then move the flare into position using trunk rotation. Painting around the trim on the left hand side of a doorway? Make it so the bristles flare to the right and into the trim. Cutting in around the ceiling, make them fare into the ceiling.
I always use an extension handle long enough that I can have both hands on the handle when rolling (broom handle will work) unless I physically can't (like painting in a hallway). For one, it is easier and two, it makes mistakes harder. If you use the extension correctly, you will almost never make a mistake while rolling. When painting the top part of the wall, get a comfortable distance from the wall and then move your top hand into a position so that when fully extended, the roller will finish within the area of the wall you cut in but short of the ceiling. If you hold the handle too low, it is very easy to accidentally go to far and hit the ceiling. If, at your arms full extension point, the roller stops short of the ceiling, it's near impossible to hit the ceiling. You can now safely roll out that area without worrying about hitting the ceiling. When you finish that area, move on and again check that when your top arm is fully extended, you will still stop short of the ceiling. This theory works great adjusted for painting ceilings and painting the bottom of walls near baseboards.
Mistakes and drips happen. Use a drop cloth and carry a rag with you. Immediately wipe up paint that accidentally gets on trim, ceiling or wall that you don't want. Especially if it's a darker color that got on a lighter color. You may still have to touch up that area but it will be easier if it has been wiped up. Have access to some water to help remove critical mistakes (assuming latex paint). Depending on the flooring, sometimes drips are easier to let dry and then peel up than to clean up immediately. Most bad paint jobs are a result of not cleaning up mistakes and leaving the results.
