We have had great success with Salifert (except PO4).
ELOS and LaMotte are also excellent kits, but as bad_coffee stated, for the price vs. efficiency the Salifert is a better deal.
Let me throw another kit into the mix. We've been using Sera test kits. The test results for the Sera vs. Salifert are the same! Our feelings are why bother paying for a more expensive kit like ELOS or LaMotte if the results are the same as the Salifert? Now the same question can be asked about Sera vs. Salifert. Why pay more for the Salifert if the Sera kit produces the same results? Much more cost effective.
One of the reasons I have problems with Salifert is possibly their location in Holland. Invariably there is ALWAYS at least one of their more popular tests that are backordered from every vendor or wholesaler at the same time. Salifert, as a company, just doesn't keep the inventories properly stocked at their distribution centers.
IMO, cost vs. effectiveness is now Sera above all the others.
Russ