Opening xhtml is slow and get big memory leak.
Below description of few open/close file test and results of memory consumption

1.Start of eclipse with no editors
heap memory usage 17MB
non-heap 38MB (CMS PermGen 35MB)

2. Open new empty xhtml
heap memory usage 37MB
non-heap 54MB (CMS PermGen 49MB)

3. Close newempty xhtml (no editor windows)
heap memory usage 35MB

4. Open simply xtml (only html tags)
heap memory usage 44MB
non-heap 57MB (CMS PermGen 51MB)

5. Close simply xhtml (no editor windows)
heap memory usage 42MB

6. Open complex xtml with non html tags
heap memory usage 56MB
non-heap 58MB (CMS PermGen 51.5MB)

7. Close complex xhtml (no editor windows)
heap memory usage 49MB

Finally I got no open windows and heap usage grows from 17MB to 49MB.
In big project with many files it is serious problem.

In Eclipse without JBossTools I don't see this problem