I've had a soft spot for these fellows for a while now, but it seems the model range is somewhat limited. Should I be bothered doing that, or should I wait for a re-vamp?

hmm, its probally worth waiting to see if they do get a re-vamp, harlequins tend to be pushed aside by GW

Realisticaly I highly doupt Harlequins will ever be made into an official codex unless there is a real push for it by gamers. If there is a Harlequin Codex coming in the future however, it would be a while off methinks.

If I were you I'd wait untill the new Eldar minitaure range comes out with the codex. My guess is it will mostly be aspects that are re-released, but you could then convert yourself a Harlequin force.
I've converted mine out of the Storm Guardian sprue mixed with Dark Eldar warrior sprue mixed with whatever other little Eldar looking bits I could find. I also use a slightly converted and interestingly painted Warlock model for my Shadowseer. Having an army that is practicaly 100% converted in some way or another is a great project and I strongly recomend it if you want to start a Harlequin force.

I am currently in the process of figuring out how to convert a really impressive Great Harlequin, and I am thinking a Swooping Hawk cross Banshee conversion.

Cheers, Cal

well if you want a really impressive great harliquen try sculpting one, i somehow think if i were to get me some halequins id order the models online from GW