If you stay with a mainline brand like Halo, you will always be able to find replacement trims, and you will have a wider selection of trims to choose from. Your local electrical supply house may have another brand that they stock. Stay away from the home stores.
Where are you using this? Many municipal codes do not allow recessed lighting at the main light source in kitchens or bathrooms. It is quite INEFFICIENT in terms of providing general area illumination. It is really meant for accent and mood lighting.
Low voltage mainly allows you to use smaller cans that use the MR16 bulbs. The bulbs are expensive, and the transformer will occasionally have to be replaced.
Consider using fixtures which are set up for the plug-in compact fluorescent bulbs.'