"Good" is very relative. It all depends on what you want out of your hard drive. Do you want speed? Do you want size? Do you want reliability? Do you want economical? All of these things need to be considered and factored into your decision.
Um.. I want it to be fast, but too fast wouldnt really matter cause i've only got 1GB Ram (upgrading to 2GB) and a 1.6GHz Dual-core. I think 320GB would be enough space and i obviously want it to be relaible. Thats about all