I never cared much for the valkyrie. Fs1 touted it more as a superiority fighter than an interceptor. Fs1 training missions didn't show you how to target bombs and all that good stuff that's handy when you're flying intercept. I didn't get the idea to use bomb targeting until i went across the fs2 interceptor training missions where they actually gave you some very good ideas when flying an interceptor.
Fs1 randomly hands me an interceptor, i treat it exactly as a fighter until i discover it is an interceptor. In which case i regard the valkyrie only good for intercepting for it's weak ass hull and shields. I never used the valkyrie at all until i discovered it's real purpose as an interceptor in fs2 training. Aside from that it wasn't much better than the serapis, so hell if i want to fly with it as a fighter. I much better like the perseus. It actually can fight, and is awesome at intercepting.
The short answer to the valkyrie for me is that a tool is more effective when you know how to use it.