I did use Spekta 1 for about 4 years and was always very happy with the results, In august 07 I started with Spekta2 (350lpi & 650lpi), it is super... we use it for about 45% of our jobs.
We also use the multiscreen option (spekta for the images and AM-screening for the vignets and tints) It cost a bit more time in prepress but it will save you a lot of wash-time on press.
And yes our clients are pay more for this extra quality.
can you elaborate a little the use of spekta 2 (350 & 650 lpi) im new in TF.How you calculate the dot gain?i check the system there is no default calibration curve to start with.not unlike in prinergy (harmony) there is a point that you can start with.