I've used a few of these (and own a 30V, 10A at home for higher current work). The noise and performance is not as good as power supplies like the agilent/TTI etc. However, it is good enough for 99% of electronics projects, unless you are constructing audio amplifiers that are very sensative/intolerant of ripple. And if you are, a few capacitors across the rails will probably make it perform far better. The construction isn't that bad overall, and I've never seen one develop any fault that could be dangerous.
If you are looking at that price range I would suggest avoiding Mastech power supplies, have seen lots of them DOA-although would be curious to hear other people's experiences with them.
And after not too long you'll probably end up with lots of different power supplies around, having one power supply with dual rails or 10A on a single rail can be very useful at times