Well, I think it's bugs:
1)Ctrl+B shortcut dosn't synchronized with button ‘Maximize pane’, so pane can be not maximized, but button pressed and vice versa
2)W on the split view, when in Display option “Apply operation to all split views ” unchecked, dosn't synchronized with icon on “Display geometry” and with “Draw” list in Display options
3)RMB click on pane tabs show radio checked for CURRENT tab, but changing it pane type changing for pne tab UNDER cursor, and AFTER this change RMB on pane tabs show radio for CHANGED tabs, but not CURRENT and not under cursor
4)Alt+/ close pane TAB, not PANE
5)Ctrl+W, Ctrl+B dosn't work for help pane tab, but in pane tab operations menu this menu items work well.
6)from SELECT tool shortcut Y for Show Handle tool dosn't work, only Enter, but from Scale, Move, Rotate- both Y and Enter worked
Am I right?

1, 2, 3, 4 appear to be valid bugs and should be submitted to SESI via
http://www.sidefx.com/index.php?option=com_content&task=view&id=768&Itemid=239 [sidefx.com]

5 is a special case since the help browser is technically a separate application which related to firefox/mozilla.

6 isn't really a bug. t/r/e are transform tools while enter brings up the node's handle. (Which might not necessarily be a transform handle.) The y key allows you to toggle between the different modes a node handle supports.

I submitted to SideFX - no reaction
5) It's strange a bit. Sometimes for help pane works well, sometime -not, one time houdini crashed. I found rule (hm….) - if first try to use Ctrl+B on any other pane tab on the pane where help pane is, then AFTER Ctrl+B works for Help pane tab well. If try to use Ctrl+B for help pane tabs without this - dosn't work. Really there more - it's related and for Alt+Shift+C for “Tear off Copy” - works in similar manner, after trick I provided. Switch between tabs using Ctrl+(Shift)+Tab or Ctrl+PgUp/PgDown works only if it started not in Help Pane tab - then I can swith to Help pane tab and from help pane tab. But if I try to begin from Help Pane - dosn't work…
Other suggestion - for “Take list” pane tab Ctrl+B works only when mouse over the toolbar for this pane. When mouse is in the pane- dosn't work
Other bug…
6)I think you don't understood me. Yes, Y is toogle between handle mode. But not only. In some videotutors, for example from 3D Buzz and Digital Tutors, claimed that Y is shortcut for “Show Handle”. I try it… Yes with “Show Handle” tool Y toggle hanlde mode. In Move/Scale/Rotate tool Y switch to “Show Handle” tool, and then swith between handle mode for Handle tool. It's now switch between M/R/S and SH. From Select tool Y dosn't switch to Show Handle or M/R/S, only Enter switch to SH. So may be it's not bug, but it's confusing…