MARNUS .... Namibia is well worth a lot of "visits" .... if you don't mind the long drives ahead. The most traffic we encounted included MANY S.A. registered overlanders / 4x4 enthusiasts & HUGE trucks (which don't leave space for any errors on the road).... and an "overzealous traffic officer, just outside Grunau... BE FOREWARNED ... stick to the speed limits
Unfortunately, we did not receive any discounted rates, and had the additional "gate entrance fees" to pay, on entering the Etosha.... nothing too serious. The camping fees were paid 1-2 months ahead of time, via e-mail. Okaukuejo and Halali being cheaper than Namutoni (which is REALLY worth a visit).... as an answer to your question, I would definitely visit these 3 again... value for money and comfort of ablutions and campsite (only the private Kwando camp and the game park outside Windhoek had "more-luxurious facilities... & less dusty)"
There are certain local towns that one needs to take a little caution in, and some that are absolutely great to stop and have a refreshing meal at, as well as a recommended change of driver / or breather.
The roads (and gravel roads) we traveled on in Namibia were better than our other neighbouring countries. I only had to reduce the tyre pressure to 1.5-1.6 bar on 1 or 2 of the "side gravel roads" in the Etosha Park.... as with the "off-roads" to the Kwando (or any other gravel road in the Caprivi).... It was great, not to have received one puncture for the entire trip...
I would say that one SHOULD have an off-roader, if you tackle ANY gravel road in Namibia, though there were some very "slow" sedans / city slickers that did attempt (with great discomfort to their cars & themselves, I saw).... Having said that, I DO think a 4x2 bakkie, with reduced tyre pressure, ample packing space and a "more reasonable fuel consumption" should also be able to do more than 60% of what a 4x4 can do.... Just remember, you DON'T have the same traction to a) travel at a higher speed on a "good" gravel road, and b) DON'T attempt ANY wet / muddy or soft sand areas ... full stop ... !!
June has excellent warm days, very cold nights (but easily sorted, if you an electric blanket or a warm water bottle for your tent) ...

, and little thick vegetation, so you can see the game better...
N.B. - get an up date on the food items that are not allowed - either entering Namibia (for the Namibian compliance,
NO RED MEAT may be brought into Namibia - at this moment),
OR, for the
S.A. re-entry ( ie. presently no fruits nor vegetables may be brought into S.A., and any in possession, MUST be handed in at the S.A. borderpost, as there is a "foreign" invasive fly that could devestate our local fresh produce crops)
The campsites were also less than 40% full .... another big plus.... the ablutions were clean and mostly all to oneself....