I'm interested in trying out this method but I don't know which system to buy or what the technical limitations are. I'd like to hear from people who've used the technique. I'd be measuring NO production in frog tectum in response to visual stimuli.

Sudin-
Direct measurement of NO is extremely difficult because concetrations on usually at the nM level. Other major difficulties in biological NO measurement include sample acquisition because the presence of oxygen will rapidly degrade NO. Therefore, you have to capture NO as soon as possible after its formation-not easy to do.
There are a number of indirect assays, most of which rely on correlation and detection of by-products during cellular NO production

These indirect assays are reviewed well in the following publication:

The FASEB Journal, Vol 7, 349-360 (The Federation of American Societies for Experimental Biology)
Measurement of nitric oxide in biological models
by S Archer

good luck!