Anyone ever used those carpet cleaners you can hire at most supermarkets, Bunnings etc?

Rather than clean out the whole house at once for a pro to come in, the idea of doing it perhaps a room or two at a time appeals to minimize inconvenience.

No specific problems, just think some areas need a freshen up after years of kids.  It is a large (?) house (about 180 m2 of carpet) but knocking it off a bit at a time feels entirely doable.  On-line search seems mostly positive.   Any feedback on these machines and any hints/tips appreciated.  

Pro's seem to all want to do the whole job all at once, and the daily deals all look good at first but the price quickly increases when they find out area needed.  I didn't think it was too far away from normal these days, but the carpet cleaners all seem to think the average 3 bedroom house is something like 80 m2, and base their advertised prices on that.  A little disingenuous I think.   

Thanks