How many slides and what do you want to use the results for?
If you have hundreds of slides then a Nikon Coolscan V with a batch slide feeder is the business - buy on Ebay, sell when you are finished. Even if you keep it, it will be cheaper than getting the slides scanned.
If you have a few tens then
AFAIK the top-end of the flatbed scanners (the ones with D-ICE) do a very good job.
Those new cheap scanners are cameras rather than scanners, I have no idea how well they focus, how fast they are in use and they certainly won't be able to do any dust removal from the scans - that's what D-ICE does though unfortunately it doesn't usually work with Kodachrome and those card mounts shed dust like no-bodies business...