Try adding noatime to the end of the UUID option:
//192.168.10.155/X /media/ewang/XShare cifs username=me,password=password,uid=1000,noatime 0 0
Then reboot and see if the behavior changes.
There are a lot of things that can cause network share slowness. You might need to become an expert on cifs to troubleshoot this issue. Because Windows is serving the files, and I don't use Windows, others will have to suggest troubleshooting from the Windows side.
There are a lot of switches that control CIFS mounting behavior:
Proceed carefully, and make note of what switches you have tried and what the behavior is.
sudo apt-get install cifs-utils
Also, check the cabling to and from the Windows machine. It's possible that it is a simple network connectivity issue. If it's a wireless connection, then you might have interference issues.