What's the quality loss?
I haven't checked closely for that, and considering all other quality factors involved I don't worry about it. Keep in mind that if you work directly in HDV format then all of your applied effects are also limited to that level of quality, whereas working in an intermediate codec gives you more overhead for effects so you might actually get better results.
And just to repeat what I said in an earlier post, an intermediate codec should give you better performance on any computer no matter how powerful - the only question is whether you need that extra performance compared to working on native HD files.