From a medical perspective, people with diabetes, renal insufficiency, or a family history of either should use caution because of the increased burden creatine places on the kidneys, especially when loading. The large amounts of sugar associated with some products can cause issues as well. I use a sugar-free creatine, (Trac by MHP) which is time-released and driven by nitric acid instead of sugar.
The purpose of a loading phase is to get you up to optimal levels fast, BUT you don't have to load. If you don't load, it will just take you longer to get your levels up and start reaping the benefits. A person who loads will notice the effects in 1-2 weeks, where a person who doesn't load may take 3-4 weeks. If you are worried about the loading phase- SKIP IT.
If you're going to use it long-term, it would be best to calculate your exact dosage requirement. Taking more than you need won't give you a greater effect. Your body will just excrete the unused portion in the form of creatinine, to the dismay of your kidneys.
Here's how to calculate:
"During the loading phase take 0.3 grams of creatine monohydrate for each kilogram you weigh. The maintenance dose is 10-times less, or 0.03 grams of creatine monohydrate per kilogram of body weight. To calculate you creatine dose in pounds simply divide your bodyweight in pounds by 2.2; 1 kilogram = 2.2 pounds. In other words, an "average" sized male of 154 pounds, weighs 70 kilograms, or 154 divided 2.2. The next step is to multiply your weight in kilos by the appropriate dose. For example, our average person would load with 21 grams of creatine monohydrate per day (0.3 x 70 = 21) and maintain with 2.1 grams of creatine monohydrate daily (0.03 x 70 = 2.1)."
Hultman, E., Soderlund, K., Timmons, J. A., Cederblad, G. and Greenhaff, P. L. (1996) Muscle creatine loading in men. American Journal of Physiology Volume 81: pages 232-237.
Personally, I cycle off every few months for two reasons: One, I'm one of those guys who gets "puffy" when I'm on. It's nice to look a little bit bigger from the increased cell volume, but it's almost like lying to myself. Cycling off lets me see where my progress is really at. Two, creatine is naturally produced in the body. I haven't seen any conclusive evidence that taking supplemental creatine can hinder your body's ability to produce it, but you never know. I would just rather play it safe.