I've done slides from digital files from time to time but always hated the process. The price per image was relatively high and the turn around time somewhat slow... but the qualtiy was good. The lab I was using got out of the E-6 film business altogether and I hadn't been happy with any alternatives since until recently. I spent some quality time with Google looking at various service providers for this sort of thing. I found
iprintfromhome.com . Very quick and easy to use their services. Get an online order to them early in the day, its completed and shipped out the same day. Something like $2.50 for the first slide and $1.50 for dupe originals. That's better pricing and service than I've recieved from any other lab and the quality is at least as good as any others I've used... without getting into LVT output which is a whole other arena.
I use this for providing slides to artists for juried art shows. The original art documentation is all done digitally but occaisionally the artist needs a number of slides as well. This is an easy, cost effective solution. Myself and two others have sent a few orders through this place in the past couple of weeks with good results. It's worth a try to see if fits what you need.
Bob Smith