Shimano BB-UN300 68mm Square Taper Bottom Bracket - English - D-NL Chain Case - 122.5mm

I also had a bad experience with this bottom bracket used on a commuting bike approx twice per week for 3 years. Today the BB failed totally and bearings fell out all over the floor when I removed it!

Avoid. I've had two of these fail now in less than 18months on a bike that has light use once a week or two. Looking around the web at other reviews I am not the only one. And unlike the old BBs which failed slowly over months these fail catastrophically on a ride leaving you with no option but to push the bike.
I took the most recent failed unit to bits and the reason was immediately clear. There are two bearing in the unit, one a poor quality sealed cartridge bearing on the none drive side, and on the drive side an open cage bearing. An open bearing in a BB! Basically this part of the bike is regularly exposed to water and salt which will quickly wash any grease out causing the bearing to fail quickly.
This is clearly planned in obsolescence meaning a regular supply of these units to landfill, or recycling if people can be bothered. Shimano should be ashamed of this sort of design practise.
Do yourself a favour, avoid this product.