Gloves serve to protect your hands from both the weather and injury. As well as being thick enough to cushion your hands in the event of a fall, they should be comfortable, allowing you to use all your fingers, and at the same time allow unimpeded access to the motorcycle controls.
They are available in many different brands, styles, materials, temperature ranges, and degrees of protection. Generally they are either made of leather or textile and come in varying lengths; the gauntlet (as worn by traffic police) which reaches halfway to the elbow, and the shorter wrist-length type. Gauntlets are warmer, but unless yours are fitted with an elasticated skirt, rainwater can run down your sleeve into the glove.
Look for decent stitching and padding, especially in areas that will absorb impact like the palms. If they are made of leather, this should be of a good thickness; new ones will feel stiff and unyielding, but will become more supple in time. Nowadays gloves are available in a combination of both leather and textile materials and can contain Kevlar panels for additional protection.
Good quality items generally have a chamois leather strip on the index finger of the left hand, for wiping rain off the helmet visor; some even have a tiny rubber strip which can be used as a "windscreen wiper". (Also available nowadays is a "rain wiper" - a rubber tube with a wiper blade - which simply slides over the glove's index finger. However unless you actually sew this on, be prepared to buy lots of them as they tend to fall off unnoticed. Don't ask me how I know.)
If you ride in hot conditions, a thinner "summer" glove should suffice.
In cold conditions, you should ensure that your hands are kept warm, since frozen hands can lead to sluggish use of the controls with a consequent reduction in safety. Heated grips can be useful here.
I tend to suffer from poor circulation in my hands anyway, and even with heated grips I found that my fingers became extremely cold. When I had the Yamaha, I purchased some Widder electric gloves. They worked fine, but only lasted about six months.
After some further research I came across another manufacturer, Gerbings.
What a difference! What impressed me with the Gerbings was the lifetime guarantee offered, so I duly bought a pair.
They only worked for a couple of months so I bought another pair to use whilst I sent the first pair back - these were replaced without question, Gerbing saying there was a manufacturing fault.
To cut a long story short, each pair lasted only a few weeks before the heating stopped. EACH TIME they were replaced straight away - I must have had at least 8 pairs! I can certainly recommend their customer service They have now sorted out the manufacturing fault so the gloves last much longer.
In January 2007 another pair failed and were replaced under warranty. These lasted until January 2008 when they were again replaced under warranty.
Update: In November 2012 the gloves again gave up the ghost and were sent back to Gerbing. Just before the end of December, a parcel arrived containing a brand new pair; and this pair even have a pocket in the sleeve section which can be used for a small 12V battery! At least I'm always up to date with the latest model!
Now bear in mind that mine saw daily use, no matter what the weather. If you're going to be buying heated gloves, get a pair of Gerbings. And no, I'm not getting paid to say that, more's the pity!