I think part of it depends on your cat, some can be very fussy and refuse to use a tray if they don't like the litter!
I've tried quite few and I'm now using the Tesco version of Catsan. Looks the same, works the same, just costs a £1 less per bag. I have to clear the trays at least twice a day otherwise they do smell, but I only change the litter once a week, sometimes I can even get away with leaving it for a fortnight. I do have 4 litter trays though, two very deep open trays, and two covered ones. I end up sweeping scattered litter most days!
My cats were not impressed with the very fine litter that looks like a cross between sand and gravel and only reluctantly used the tray with it in when the others needed clearing. I wasn't impressed when I discovered that unless you clear out clumping litter within a few hours, the whole lot sets like concrete...
The Dr. Martin's stuff seems to work quite well (I think there are other brands of crystal litter too) but you have to turn it over daily otherwise the urine won't evaporate (or whatever happens to it) and it will just puddle in the bottom of the tray and smell.
You can get litter deodorisers so that you can't smell noxious niffs from the tray - kitty will though, so you'll still have to clean it and change the litter regularly, otherwise he'll find an alternative spot...