None of my hard drives is faster than 7,200 rpm, so I can't really say. I should think RAM would be far more important to a gamer.
Speed would be important when writing, say, uncompressed video files. Then it would be a bottleneck, but not really problematic. Normally you'd use a non-linear editor that could deal with compressed files. Otherwise, you'd recompress as the file is being written. (Uncompressed video files are enormous). So, in summary, no, I don't think it's terribly important, but if someone else knows more about it, by all means educate my butt.
SATA/150 (SATA 1) is comparable to PATA/133 in practice. Your motherboard will have no problem with it. SATA is designed to be backwards and forwards compatible.