I also used to use Informant before the advent of computers (and used to annotate for them, too), I have a collection of the first 90 or so in my bookcase, but I haven't looked at them since. I think they belong to the past.
I remember checking some important games in the last couple I received, but most of the games had already been annotated in Chesspublishing and Chess Today several months before.

the Informant is in some ways like Chesspub, a collection of annotated games. Like Watson says in his TWIC review,  i find the electronic PGN versions useful. 

Benefits: 
-Annotations are by top players. This is really the Informant's main selling point. 
-Its' more topical than Chesspub, in the sense that more games are annotated in the critical main lines of 1. e4 and 1. d4. But this may vary for different sites and users. For the Caro-Kann for example, i think informant gives me alot more than Martin's site (which is obsessed about the Scandinavian). 

Drawbacks:
- Top players who annotate these games often do not like to reveal their opening secrets. 
-The languageless annotations make it more difficult for lower-rated players.

But i think an even better product (and one of my favourites at present) is CBM. I don't see why anyone will bother with informant now that CBM is getting stronger with every issue. The analysis may not be by the absolute top players, but they are done by very competent GMs (e.g. Rogozenko, Lutz, Golubev, Erenburg, Lukacs etc) who are honest and don't, for the most part, keep secrets hidden away. I also like the extensive verbal explanations (e.g. by Marin), and the fancy coloured squares and arrows (!) .

How would you define 'amateur'? Non-titled? Below 2300? Below 1900? Not playing tms?

Anyway, to benefit from Informator I'd think you must be playing the main lines of popular openings against booked up opposition or perhaps be young and very promising...