I've been using them for a couple of months now, but split between two basses. The E and A on my '55 Juzek are wonderful, especially under the bow. The fullest, loudest sound I have heard on this bass and I've been playing it for 30 years. I think I prefer Spiro Mittels for jazz pizz for a little more sizzle, but these work well. I have Obligato D and G on this bass and the combination is fine together. It seems that the Obli D and G are louder now, too.
On my other, older, German bass with a darker sound, I have the EP G in combo with Weichs and am very happy. More meat under my finger, less twang and darker sounding with the bow on the G string. This bass seems to like less tension, hence the Weichs.