Having used the TM LaTeX bundle to write my masters and PhD theses, and now papers (and everything else!), I can say that it is a huge time saver.  I would recommend that you also consider Sublime (I don't use it myself, but it does have bundle compatibility with TM, and so the LaTeX bundle should work nicely without too much effort).

When I was writing up my PhD I easily converted a handful of "writing-up-stage PhD students" to TM (one guy even bought a Mac for it) purely on the strength of the LaTeX bundle.  There are some old (i.e. for TM1) screencasts that are a great place to start.  They explain the basic functionality and give a feel for what's possible in the bundle: http://macromates.com/screencasts (though note that the "Project" one has changed a lot in TM2, but can easily be emulated using .tm_properties files).  Be sure to checkout the project-wide auto-completions for references (both for \cite and \ref), pdfsync and of course snippets for creating sections/chapters/equations/references etc!

You're going to spend quite a while writing, and it won't be fun all the time, so I would say that it is well worth "shopping around" before settling on an editor :-).

Good luck!

David.