Just back from Thetis. The track is pretty overgrown and has a few windfalls, but is basically okay to follow. The key marker on the Overland Track is a smallish tea tree, right on the side of the track, which has a notch with three horizontal marks cut into it. You might just make it out in mjd's photo (thanks for that info Martin). It's about 200 metres west of the first main creek out of Pelion (after the Old Pelion turnoff). Then about 30 metres into the forest is a red painted tin-lid style marker about head height on a gum tree. Thereafter you head into the scrub, making sure you take your time and sniff around for track markers (varying from tape to tin lids to reflective plastic) rather than going on a compass bearing. The scrub is thickish here and there, but nowhere near SW standard (see pic below).
After some (very welcome) sections of sub-alpine meadow, there's a second scrubby patch high up under the saddle's sedimentary rock-bands. This one is a little harder one to negotiate, as markers are fewer. Take your time and you'll eventually break out into the clear. With a little care you can squeeze under the second cliff line and avoid most of the scoparia that will try to block your way.
The camping is great - 'though water is unreliable. We found some in pools above the saddle, and there's an established soak south of the pencil pine grove where we camped. We had a glorious time, in fine, hot weather, exploring Paddys Nut, Thetis, Ossa etc. 20 years ago I also went to Achilles, Leonards Tarn and Perrins, but in hot conditions and with older bones, I didn't feel I needed to go back
The climbing/scrambling/walking is challenging but fun. These are big mountains, with huge views and boulders to match. In my experience only Pelion West (which is notorious!) has bigger boulders that Thetis and Ossa. I've uploaded some photos at
http://picasaweb.google.com/auntyscuttl ... isRMMTrip#cheers
Peter

- Mild tea-tree and eucalypt scrub on the climb to Thetis Saddle