I've been very happy with my HMC40. A couple of things to consider. I've collected a bunch of SDXC cards lately, but the HMC40 is limited to SDHC, so you only get 32GB, and files are broken up into 4GB chunks, like many SD media cameras. And yet, I don't really see a newer model I'd pick instead.
I have the audio adapter as well, for my various and sundry XLR mics. If you're doing fairly fixed interview-type shoots, you can hook a wired lav mic directly to the XLR inputs, run them from phantom power, etc. I have a couple of these, nothing too expensive, from MXL: http://www.bhphotovideo.com/c/product/581525-REG/MXL_FR_355K_FR_355K_Lavali.... I needed some for a project, these did fine (one omni, one cardioid). If you don't have the XLR module, you can find some that hook in via the 3.5mm jack.. no recommendations here.
Beyond that, if you're shooting action, you'll need some other system. Lots of people use wireless lavs; those systems are expensive, but let you monitor on-camera, at least if two inputs are enough. I prefer to put a field recorder on each subject, set it to 24-bit, and pretty much not worry too much that levels will ever be a problem. There's probably a shotgun and/or boom mic on-camera at the same time, if it's an "in-studio" sort of shoot.
Hi Carlos, we use the HMC40 at work, and it is a great camera, but it is getting a little old. I would get the newer AG-AC90. The XLR mic inputs are built-in, not added on, it shoots 1080/60p at 28mbps and takes dual 128GB SDXC cards. Only $1956 at Amazon.