I currently run 2 fluval 404s... though they work decently enough. However, when I do replace them, I will probably replace them with Rena's Filstar xP canister filters. I fiddled around with the Filstar canisters, and I like them more than the Fluvals. They are about the same price as well (cheaper in some cases). However, if you want the cream of the crop, go with an Eheim canister. Several people have run Eheim canisters for ages, and they just won't break down. I currently have an Eheim 2026 Pro running, and I love it. However, I would avoid the Eheim Ecco line of canisters... those imho are a waste of plastic.
To prevent your canister from gunking up, I'd suggest putting a pre-filter over the intake of your canister. You can buy commerical intakes like Filtermax III prefilters, or the Eheim prefilter... or you can make your own. I make my own by cutting a slot in an Aquaclear sponge, and fitting that over the intake of the filter. Clean the prefilter out at least once a week (blasting them in the sink, etc. will work just fine). Ever since I've done this, I've been cleaning out my canisters once every 6 months... rather than once every month.
HTH
-Richer