There are pros and cons.
Building with METEOR might be very smooth and very harsh at the same time.
The former is due to the functionality of METEOR - your write radically less code, you use the same language for the client and for the server and you can port apps on mobile with just few commands. Also, METEOR is reactive - whenever the persistent data changes, the views are updated accordingly.
Using the account system, with one line of code, you can have login, logout, account creation, email validation, password recovery, and login with OAuth providers like Facebook or Twitter.
I did the same in a nodeJS app using password (npm) and it took me more than a week.
On the other hand, METEOR is relatively new and even though you have already a decent online METEOR community, it is still not as big as Ruby or NodeJS one. It makes METEOR sometimes a pain in the ass, as you try to do a simple thing, yet you are looking for a solution for a few hours.
Also, I personally do not like not-relational databases and METEOR is bound to MongoDB. Not relational databases give you the flexibility to store data in any form, which will eventually lead to bugs. Fixed schemas not only prevent that, but also can serve as a good documentation about how you model your data. However, this part is highly opinionated as I have spent 3 years at SAP where OpenSQL and relational databases play a major role.