Funny that you should ask, I just started toying with kernels myself. I'll share my observations, but I don't know if they will apply to your phone. The two big advantages to flashing a different kernel are CPU speed and battery life. The kernel has to support the CPU speeds you are looking for. For my phone, the stock kernel will not allow anything above 600MHz. Other kernels will go well beyond that (I think 1300MHz for my phone, but I'm at 1100MHz). Some kernels will allow a minimum of 125MHz, others won't go below 300MHz. And, I think finally, the voltage of the kernel can be UltraLow, Low or Medium.
Here's what I believe the advantages of each to be: Lower voltages and lower CPU speeds translate to improved battery life. Higher CPU speeds (this I am certain of) mean improved performance.
The best situation is to find the lowest voltage kernel that your phone will run well on (still be responsive). Mine has proven to be Medium, so far. Also, the lower you can set your minimum CPU speed at, the better. For my phone, setting it at 125MHz on one kernel is just fine. For other kernels, setting it at 125MHz makes it all but unusable. Usually, the upper limit of the CPU will be determined by how hot it runs at that speed. Mine seems to be fine at 1100MHz, so far. It may be able to run reliably at 1200-1300MHz. Ideally, I'm looking for an UltraLow kernel that could be set at a low of 125MHz and a high of 1300MHz that my phone would run well on. Right now, it's Medium, 300MHz and 1100MHz.
Lastly, I have not found it necessary to wipe anything when flashing a new kernel. The nice thing about that is a lot less restoring of apps, etc. when trying out a new kernel. Also, every phone is different. Mine will not run on any ChevyNo1 kernel. Other phones are just fine with them. The 1100MHz kernel from jdlfg (available through ROM Manager) is working well for me right now. Most importantly, make a backup of your current ROM and kernel before doing anything. It will save your bacon at some point. Good luck.
