Ph.D. admission in the US/UK: How is an M.Sc. regarded? In the UK/US people usually don't get an MSc before pursuing a PhD in math.
But in other countries getting an MSc before the PhD is the more common case.
This raises the following questions regarding how graduate admission committees view applicants with an MSc from countries where it is common to get one.
On one hand, seems like an MSc is another "proof of my abilities". On the other hand, the committees may ignore it altogether because they have to compare the applicants by their greatest common ground.
When talking about an MSc I mean a two-years program with a thesis.
Can you compare the relative importance (admission-wise) of:


*

*Course grades (specifically, how important are BSc grades and how important are MSc grades? $(*)$)

*MSc thesis.

*Recommendation letters.


In respect to comparing $(2)$ and $(3)$, I can either try very hard to write the best thesis I can, or alternatively, I can work, in addition to my main thesis, on some smaller scale projects with one or two faculty members other than my advisor, to make sure I get more than one sincere recommendation letter.
$(*)$ I need to know this as I have some freedom to choose which courses will appear where (I have completed more than enough credit during my BSc studies and can move some of the graduate level credit to the MSc).
 A: I have been Dir. Grad. Studies in Math in MN in two intervals, and also have an understanding of others' perceptions:
Letters of recommendation are the most important... tho' low GRE subject test scores can dissuade some admissions committees. (My own attitude is that the GRE's multiple-choice stuff is not-at-all reliable... by now I'd look at GRE general-test verbal... ! ...)
GPA is not of much interest. Sure, crappiness in not-so-hard classes is not a plus...
GRE subject test is the easy indicator for lotsa lazy admissions committees to look at. Bang-there-you-are. 
It is true that letters of recommendation from people who themselves have dubious mathematical judgement are iffy... No helping that, if one is from a remote place. 
A "personal statement" that shows that you understand that there is a larger world... is very good.
(Good luck with this very tumultuous part in anyone's life...)
A: I would say:


*

*Your grades in your MSc are probably more important than your undergraduate grades.  Ph.D. programs are looking for evidence that students can succeed at graduate-level courses, and the best possible evidence of this is previous success at graduate-level courses.

*No one on the admissions committee will read your master's thesis.  The quality of it matters only in how much it affects your letters of recommendation.

*Letters of recommendation can be important, especially if you can get a professor to write a particularly glowing letter for you.
Roughly speaking, Ph.D. programs are looking for very high grades, good letters of recommendation, previous research experience, and high scores on standardized tests.  
