As I said in my earlier post, when I open a wine that needs decanting, either because it has significant sediment (and I consider any visible sediment to be significant) or because it's quite young, I generally decant the wine into a 4-cup Pyrex measuring cup, then dump the gunk left in the bottle down the sink, rinse the bottle and pour the wine back into it (the process is called double decanting).
I don't use a fancy decanter unless we have guests for dinner, and even then I prefer to double decant so they can see the label. Also, the decanter doesn't fit in the wine coaster too well.
Double decanting would be preferable if you intend to drink only half the bottle since the bottle can be recorked for short-term storage. Decanting half of the bottle would make little sense as it would leave the gunk in the bottle.