It feels like I have painted miles and miles of trim........
In my opinion, I think a uniform trim color throughout the house looks best. I am partial to an off-white semi-gloss as mkksmom mentioned. Ditto the angled brush. Frog Tape is much better than regular blue painters tape but I have yet to achieve a perfectly crisp edge, I always get some amount of bleeding.
If you want really nice transitions between the walls and trim, use a paintable chalk. A little goes a long way. Keep the tip openning really small, lay down the least amount of chalk as possible. I keep a cup of warm soapy water and to smooth the chalk (and force it into the joints) I dip my finger in the soapy water and smooth the chalk down in one smooth, constant motion. It take a bit of practice but it is really pretty easy once you try it a few times. Ask at the paint store for a chalk recommendation, they can direct you to the type to use.
I would stay away from oil based paints. I used them for part of our house and I really think oil is best left to the pros. For me, oil set up too quickly and it was very unforgiving, I could not go back with the brush to even out the paint. Also, I hated having to clean up with paint thinner.
Follow Mothering