Your choice of tour operator and your choice of climbing route are probably the two biggest factors in determining the quality of your Kilimanjaro experience.
Kilimanjaro park regulations require all climbers to be accompanied by a certified guide, and follow established routes. Your options are basically to hire a private guide for yourself and your group, or to join an organized trekking group.
If you are going alone or as a couple, we suggest joining an organized group. People who climb Kilimanjaro tend to lead interesting lives, and part of the fun of a group trek is the social interaction with the other trekkers. You will be spending much time in camp eating and just hanging around, so it's nice to have some travel companions.
To some extent, you get what you pay for on a Kilimanjaro trek. A budget tour operator will probably serve only basic food, and their tents and other equipment might be in poor condition (or you might have to bring your own gear).
At the other end of the scale, we ate like kings at folding tables and chairs in bug-proof mess tents on our Kiliwarriors trip. They also carried a shower tent, and a portable toilet so that we didn't have to use the smelly long-drop outhouses (these were the envy of the other groups on the mountain, and more than a few clients from other outfitters tried to sneak into our toilet tent!) Kiliwarriors also carried a satellite phone for emergency use (and for calling friends from the summit!),
as well as extensive safety gear such as an inflatable hyperbaric chamber for severe altitude problems.
There are lots of good Kilimanjaro tour operators out there (and more than a few bad ones too!) Two that we recommend from personal experience are: