If you're leaning over your desk to talk into the mic, your back is going to start hurting, and this will reflect in your voice and your mood, which will come through loud and clear on your podcast. Find a place for the mic, even if you have to prop it up on books or take it from its stand and just hold it. You need to be comfortable for your voice to sound the best.
Some people believe the best way to record is to stand. Standing increases your energy levels, and you may feel more comfortable if you can pace. Mur has had comments from listeners that her tone was completely different on the podcasts where she stood and recorded with her handheld mic and iRiver than those where she sat down with her computer and mixer. Some mics will not allow standing, however, so you may want to keep that in mind before you buy. If you do stand or walk around, think of investing in a wireless headset. Whatever you end up doing, test the sound of the mic while moving, making sure it doesn't pick up any background noise of your movement, whether it be your walking or the mic brushing against something.