I have been using glass carriers for the last 15 years. Combined with a laser alignment tool, the glass carriers deliver the best overall sharpness without a doubt. Cleanliness is certainly an issue, especially if you use a condenser enlarger, but it is worth it in my opinion. I would love to replace the lower glass in my Saunders 4550xl glass carrier with coated glass but haven't found any likely candidates yet. I doubt I would see much improvement at this point with the coated glass but every little bit helps.