It's an impressive project, but I'm not sure the niche is big enough. It's certainly come a long way since the last time I looked at it!
My biggest concern is that Seq sucks users into a sort of local maximum. While piping syntax is nice, and the built-in routines are handy, it's a lot less flexible than a "mainstream" programming language, simply because of the smaller community and relative paucity of libraries. BioPython[1] has been around a long long time, and I think a lot of potential users of Seq would be better suited by using a regular bioinformatics library in the language they know best.
e.g: The example of reading Fasta files in Seq:
# iterate over everything
for r in FASTA('genome.fa'):
print r.name
print r.seq
from Bio import SeqIO
for r in SeqIO.parse("genome.fa", "fasta"):
print(r.id)
print(r.seq)