I previously used Salifert but didn't replace them when I ran out. I don't know what is going on with Salifert, but I have heard a lot of rumors of people having some problems with newer tests and Salifert basically being unreachable. So take that for what it's worth.
Seachem is definitely not expensive, especially when compared to Salifert. You can get the Seachem MultiTest Marine Basic which includes Ammonia, Nitrite, Nitrate, PH, and Alk for around $25.00. I haven't been using Seachem long, but so far all of my readings have been normal.
I have also been thinking about trying Instant Ocean's test kit. It looks to be similar to the old Fastest brand, so I wonder if they bought them out or something. What I like about that one is they have a colored plastic sample that is placed right next to the test sample. I hate trying to compare color to a little piece of paper, so I'm seriously considering giving them a try.