Just to be clear, there is no issue if you left click, hold, and drag in the uppermost "border" region (above the PlayerBar and at the same level as the menus, customized toolbar buttons, and Close button). This is the same region universally used to drag windows. You only get Spotlight when left clicking in the PlayerBar region. The sensitive region is nicely revealed if you have Tooltips activated and hover the mouse about.
Personally, I think having a "PlayerBar long click" action is clever, but this screen real estate could potentially become even more valuable if the user could specify which action occurs. I agree with HPBME in that there are plenty of other ways to activate Spotlight, so for me it's not necessary to have it her, especially since I do not use Spotlight all that often. However, I would love it if long left click in this relatively large region could activate one of my most used toolbar buttons (which are tiny). For example, I might choose opening the Options menu, something I do fairly often, or maybe toggling the Tree visibility, etc. The "PlayerBar long click" action could be user-selected by adding a checkbox in the middle region of the Customize Toolbar popup. Alternatively, a RMB exclusive option on any custom toolbar button. Then if nothing is selected, the region reverts to dragging the window (Spotlight would have to be added to the Customize Toolbar list, or a RMB option added to its currently displayed button).
If none of this is deemed possible at this time, then I vote for leaving the current action alone since it does make logical sense to quickly open Spotlight from the PlayerBar (once you realize what is going on). It's more useful to me as is than assigning additional area for simply dragging a window.