I suppose they're okay on a budget but the 9600GT is the same price now. Well I suppose it depends on the model but for the most part they're the same price.
Haha well that depends. 9800GTX is win but 9800GT is fail. The 9800GT is the exact same card as the 8800GT, the only difference is the name and the price. The 8800GT is about $30 cheaper and since there are more of them out, you will most likely find one that is clocked higher than an 8800GT. The Tri-SLI is pretty cool, but inefficient.
It uses the exact same architecture, same frame buffer, RAM size, shader processors, core clock, and memory clock speeds. The benchmarks show it getting 2 fps higher than the 8800GT because they were benchmarking the EVGA 9800GT which is overclocked 50MHz.