The city of Hakkari itself is nothing to write home about. Lots of army quarters but everyday life seems pretty normal. Getting there makes it worth the trip, as you are literally in the most remote city of the country, near the corner where Turkish, Iranian, and Iraqi borders meet.
People seem to be indifferent to tourists (or perhaps just a little cautious) but usually react in a friendly way if you want to take their pictures. You may hear other languages besides Turkish due to high level of illegal immigrants from the borders. But they are mostly not dangerous.
Frequent buses from Van make Hakkari easily accessible.
As Hakkari is not a big place most of the town is within walking distance. (But do read the "Stay safe" passage.) It does spread out, however, over various hills.
Hakkari has three hotels. None of them has its own website.
All room prices are for single rooms as of Decemmber 2013.
Travelling there is pretty safe as long as you stick to the main roads and/or use public transport. Going for a wild walk (to take pictures) on your own even to the top of one of the hills close to the city could let you end up next to a military zone. That could be very unpleasant as you may be thought to be a PKK agent and treated as such. You should always have your passport or ID with you. To a soldier who has been designated for the security of the land to stay in these regions (not the most comfortable place to be deployed), it seems to be difficult to differentiate between a tourist and a terrorist.
(+90) 438 is the area code for Hakkari.
Check with big bus companies like Vangölü (☎ 0438 211 43 24) or Best Van (☎ 0438 211 67 34). Due to the regional conflicts there might be ID controls on the buses. In case of bombings roads might also be closed, so do not rely on too tight a schedule.