Was there 2years ago. Went in July which is winter for them - and weather was fantastic. It was about 25 during the day but dropped down to 3 or 4 at night.
We went on an organised (mix of camping and chalets) trip so I cannot advise very much on accomodation options. The company we used were Wildog Safari and we found them very good. They also do a chalet only trip for those who want their home comforts. You only really have a choice of accomodation in a handful of places as most places you will be are national parks and there is just the designated accomodation section (area with camping facilities and chalets). The only accom we used that was not part of our trip was The Elegant Guesthouse in Windhoek and I can reccomend this place - see it on Tripadvisor.
Self drive is also very popular, but you would need to know how to drive in sand (lack of paved roads) and should also appreciate the huge distances between places and the associated isolation if you break down. The country is about as big as France + Germany combined but only has a couple of million inhabitants so that will give you an idea. It also means that it is very safe as there are no people, therefore no bad guys to worry about
. You should however be careful in Windhoek after dark.
Out 10 day tour took in Etosha (probably the best place for wildlife outside of the Serengetti and Otavango Delta....yet costs a fraction of the price. (I have also been to Kruger and Etosha is far superior). We saw huge amounts of wildlife in including all of the Big 5.
We then continued on to the Skeleton coast which is totally different but no less stunning. Finally we went to Soussevlei (spelling?) to the amazing dunes (some of the largest and oldest dunes in the world). These areas are the main highlights of the country but there is also a popular route up from Cape town which also includes the Fish river canyon which also has points of interest.
I could not recommend Namibia highly enough. Everyone speaks English, no insects/mossies, fantastic scenary, stunning night sky and relatively low cost. The Germans used to run the place so for the most part everything works as it should, which is always a bonus in Africa. For me, it is a better version of South Africa, and I would return in a flash.
However it is a holiday that is more suited to the active holiday maker rather than the golf/resort/pool type person.
Joes Beer house in Windhoek is the main meeting spot/restaurant/bar for people at the beginning and end of their trip. The food is pretty good too.