In reply to Stephen3005: I was in the Everest region for 2.5 months from Jan to March although other times have been in October and April. A few of my thoughts on differences between January and the fall trekking season which tails off after mid-December;
1) its the best time to go to EBC. There are far few trekkers but still people on the main trails so you'll never actually be alone. A few companies organize now xmas / new year EBC trips that were almost unheard of 10 years ago. Crystal clear skies should be the norm for most of the trip but you can always be unlucky. You have to be ready for some heavy snowfall but even that won't cause you problems on the main trail to EBC. Day time temps in January are better for trekking (it gets really hot in main seasons) and still warm but on the other hand much colder evenings and nights.
2) If you are going on the main route from Namche to EBC and back the same way then solo is fine if you really want to considering risks of being alone if you get sick etc... If you plan to do the trip that BruceM did in the video he posted above (great video) then that's not the EBC route and don't do that solo, (Bruce went all over the place off the main EBC trail for a great trip of the whole area haha) go with a porter at least so you aren't alone. To go in January on those routes should only be for trekkers who are experienced and have been before and then many would have a guide /porter for a few bits of it (Renjo LA, Cho La in winter etc..)
3) you won't need crampons or ice axe for the normal EBC route even in January but I wouldn't wear normal trail shoes as many do in the main seasons but would wear light trekking boots for more warmth and incase of snow.
4) a number of tea houses close in January and re-open again in March/April but there will be many still open and you'll have no problem with accommodation at all. You'll have the pick of the best rooms at good prices.
5) take a slightly warmer down sleeping bag than other seasons but tea houses have blankets so you'll not be cold. I usually carry a bag with a light synthetic and use them together so have options for low down when its warm and higher when its very cold. Otherwise a single good down bag is fine especially if carrying your own gear and weight is an issue.
6) Good down jacket. That's needed anyway for all seasons but is often carried and not used in March/April or Oct/Nov but you'll definitely need it in January, as soon as sun goes down its really cold outside and inside tea houses unless you are close the fire.
PM me if you have any questions.
regards
Andrew