Almost 4 years ago I sent out 55 or so CVs. I received replies similar to what you say, personal letters, standard letters, postcards.
I got replies from about 1/3 - 1/2 of the companies. A note - for 3 of the 4 interviews I did the first line of contact was a phone call, often at very short notice (Like can you come in two days!). The 4th - I was emailed an application form, and then they rang me.
To give you an idea, my company had pre 9/11 over 1200 CVs on file. (Large UK charter). (Although judging by the people you will have met during your training some of those will have 3 heads! i.e. unemployable)