I recently bought a costume from them - an Admiral's costume from Nemesis-era. It wasn't perfect - I provided my measurements (which I reduced slightly as I'd heard they run too big) and specified it was a woman's costume and it was still far too big/baggy. The rank stripes on the sleeves were also far too wide and up by the elbows for some reason.
However, I had expected it not to fit properly so got it taken in by a local seamstress, who also managed to fix the rank stripes. The fabric is quite lightweight, good for conventions etc which can get quite warm, and the craftsmanship is good - well stitched, good zippers, etc. The gold piping looks great, and the red undershirt is a perfect fit.
I haven't seen or bought any of their other costumes so I can't speak as to the quality of any which use different fabric to this one. So, I'm really happy with it in the end, but if you wanted something that fits perfectly 'off the hanger' so to speak, you might be disappointed.
Oh, and here's a pic of how it looked post-alterations once I added all the accessories - it only came with a combadge, but it wasn't a very high quality one. (Fortunately, I already had one.