I've used Metrel (I own an MI3000) and Megger, but not Fluke.
I don't understand the negative attitude towards Metrel kit. To be honest, I think a lot of it comes down to "tester snobbery"... My favourite comparison is with cars. Some people insist on a BMW or Mercedes and "hate" anything else without ever trying it. If they did they'd find that the Ford Fiesta and Fiat 500 are actually pretty damn good cars! I aspire to one day own a BMW M5, but in the meantime I can't afford it and my Vauxhall Vectra gets me from A to B very comfortably!
As I said, I've not used Fluke, but by the sounds of things, the Metrel is much better equipped. In my opinion it beats the mighty Meggers in certain aspects (RCD autotest in particular, the display is much easier to read)
Cbw and ExArmy, why do you dislike Metrel?