I am a full-time player and use these exclusively from large weddings to intimate quiet gigs. I find the response and durability is absolutely stunning. I use the reeds for several hours a day and they last me for a minimum of 3 months (as opposed to cane which only lasts me for 3 weeks max). They respond in exactly the same way every single time and very evenly over the whole range of the instrument, from low Bb to altissimo. No need to wet them, they don't warp, you don't need to warm them up.
The only downside I have found is the sound, which is very slightly brighter and a tiny bit less full than the cane reeds, however only I notice this (I have asked other musicians if they notice the difference in my sound since switching and no-one has). One other bizzare effect is that multiphonics are more difficult to get out. I find that If I have the open hole half way closed it works, but it is much harder still than with cane reeds. I do find that their strengths are very misleading. I would play a Vandoren 3.5 or 3. I think the 4.5 fibracell sits somewhere in between those.
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