My opinion on the subject is that bi-wiring *can* offer an improvement, but it depends on a few things. Firstly, bi-wiring usually increases the detail and clarity in my experience, and makes the sound slightly brighter, and the bass more explicit. However, if your speakers already sound bright, then you could end up with too much of a good thing, in a manner of speaking. So whether you do it will depend very much of the characteristics of the system, and some speakers by their nature will benefit more than others.
For example, a friend on another forum has tried bi-wiring but went back to single wiring on his Arcam + Mission combo, he said it made the sound a little too refined on his system.
On my system, I had my Wharfedale Diamond's biwired on my old Cambridge Audio amplifier. The improvement was noticable, opening the speakers out very nicely. I have since bought a new amp and for the time being at least I am back to single wiring, and the sound is ever so slightly shut-in, an effect that bi-wiring will cure completely, as I know from experience from the last time.
However, I think that the major reason for improvements is replacing the metal jumpers on the loudspeakers. Therefore I concur that a small piece of high quality speaker cable linking the terminals on the speaker will have more or less the same effect IMO.