Tab completion is vital for the LaTeX plugin to be effective. For instance, a yields \alpha in math mode, etc.; it yields \mathit{} in math mode and \textit{} in text mode. This makes for a much more enjoyable texing experience, and it does not interfere with other ST2 functionality, as far as I can tell (again, when editing tex). I always turn tab completion on. BTW if there are multiple completions (e.g. f can be \phi or \varphi), it is trivial to implement cycling among completions using the standard .sublime-completions file. I did that.
In this case, ctrl+space does nto work quite as well—it distracts from typing, and adds a bunch of completions that are not relevant.
That said, if this interferes with ST2 as a whole, I will reimplement the TextMate-like command-backslash shortcut (or something like it), although that will entail duplicating functionality that is already in ST2.
I’ll keep following development closely and adapt.
Bottom line: strong vote in favor of tab completion!