I did the Wick line from Edinburgh on a Club 55 ticket for £19 return on 8 March.
The 0706 for Wick left late because the driver didn't turn up, then we had to wait for two incoming trains - I think the first loop is at Dingwall, so once an Inverness train has left there you have half an hour to wait. Eventually we departed at 08.15, straight after the 0812 arrival.
The line loops around the Beauly Firth and the Dornoch Firth - it is much longer than the improved A( road, but the distant mountains were snow covered, and there is lots of estuary scenery, with the big oil rigs at Invergordon too. You turn inland again at Bonar Bridge, up to Lairg, with the funny little station for the YHA at Carbisdale Castle. East of Lairg you are in a picturesque crofting glen, running down to the sea again at Brora.
Sad that the stations on this stretch aren't in better nick.
We stopped for about 20 mins at Rogart halt, waiting for an oncoming train. There are railway camping coaches for hire there, and a big collection of railwayana, and a shunting loco.
Nice coastal scenery around helmsdale, with the Cairngorms just visible far to the south, and indeed the whole N coast of Moray stretching out towards Fraserburgh.
After Helmsdale you really go to the back of beyond, into the wilderness - Kinbrace, Altnabreac, Scotscalder. Very bleak, a couple of peaks and lakes. The line limit seems to be 75 in most places and he was certainly bombing along. I missed Altnabreac in fact, but managed to photo the others from the train.
Then we omitted the Thurso stop (a bus was laid on for the 2 or 3 passengers there), and headed straight to Wick, arr 40 mins late. I wanted a bit more time there so I caught the 13.46 bus back to inverness (£17 single) rather than the train at about 12.45. Mind you, the delights of Wick are limited and 1 1/2 hours seemed enough. It was cold and windy. I have been up in the car on another occasion to John O Groats, Dunnet Head and great views of the Orkneys.
The bus route south follows the coast more, and you can trace the old Lybster branch. You change at Dunbeath for the Thurso-Inverness service - that's the bus company's equivalent of Georgemas Jc.
Well worth doing, a great day out. Remember though, if you get in Inverness after the last Wick train has departed (17.10 I think), your overnight stay does not count as break of journey, and you are entitled to continue your journey by the 0706 the next day (National Conditions of Carriage). The lady at Edinburgh Waverley ticket desk tried to tell me I would have to buy an Inverness-Wick single the next morning, but I got them to endorse my ticket and arrival time at Inverness at 18.30 when we got in the night before. The Wick guard was quite happy with my ticket - they must have lots of passengers who ahve to overnight it in Inverness.