Mike,
The short answer is, yes....
I'm just past a year since my mechanical valve was put in, and I still have to take something to sleep at night, otherwise I just toss around trying to ignore it. Often, it feels like it's thumping in my throat, or up the sides of my neck.
I also get a hard thumping in my chest upon exertion, but usually during the day it doesn't bother me too much, mainly at night. In fact, for several months post-op my cardiologist had me on some rather strong sleep meds.
And I agree with the hydration - certainly seems to lessen it somewhat.
Hang in there, mine has lessened over time, although I still would like it lessened further. It does get annoying. The explanation I was given was basically that the heart had been having to work harder for years to compensate for the bicuspid valve, then more for my aneuryism. Now the heart needs to learn to back it down, it's still working harder than it needs to. Hope that makes some sense....
I take Melatonin at night (usually around 20 mg), and that helps put me to sleep, and generally stay asleep.
Hope it gets better for you soon