For amv editors, this isn't worth buying (unless you have money you want to throw at something.)
Final encoding is done relatively infrequently by most editors...so you wouldn't get much use out of it. Encoders for fansub groups might be more interested in this until my next sentence.
This card can only be used with Premiere Pro CS3/4/Elements 7, Ulead 11, DVD MovieFactory 5, WinDVD 8 (which doesn't encode in the first place,) and TMPEGEnc 4.0 Xpress.
I (and hopefully others) shy away from letting an NLE do final encoding because:
1) They typically suck at encoding
2) They typically limit encoding configuration options
So that leaves TMPEGEnc 4.0 Xpress, which also is quite restrictive on encoding options (Set aspect ratio, Frame rate, CBR/VBR/Constant Quantizer/Constant Quality, mpeg4 profile/level, CABLC or CABAC, pixel/half/quarter motion estimation)
So it pretty much misses all the marks for quality-oriented editors and fansub encoders. If it could be used with x.264 (and related UIs like meGUI) it would probably be worth it for fansub groups (who can have encode times lasting for hours upon hours, and have weekly deadlines.) For AMVs though, you'd get more use out of a cpu upgrade (as cpu is used for indexing, avisynth, vdub/mod, lossless clip encoding, editing, and encoding.)