Bad bloom is a pet peeve of mine, though it's gotten a lot better over the last couple of years.
Use multiple iterations like Spike said, it makes a huge difference visually.
Blur during downsampling to avoid pixelation, reduces crawling pixels when moving around.
Bluring with small kernel size during upsampling reduces the 'bilinear-look', incase you can afford it.
Don't use straight addition in LDR, it blows out stuff and creates garish colors, prefer 'screen' blending or something similar.
Subtract unblurred frame from blurred for certain things (eg. sky lighting spilling over edges).
Google for "Kawase" light streak filter for filter with a less uniform look.
You can select brightest pixels in low res buffer and splat pointsprites (inferring color).
Don't overdo it
![Razz :P](./images/smilies/icon_razz.gif)