Even though our Macs are set up for wi-fi (we use an Airport network at home and work), I find myself reaching for the Ethernet cable in the closet at most Marriott's which have both choices. I set up our networks and know most of the tricks, but these wi-fi's have consistently confounded me, as a Mac user. No problems whatsoever with the Ethernet broadband. Our laptops have both the xxxb and xxxg technologies for wireless, but to no avail.
I haven't used the pay as you go services, rather the free services at the select service hotels. I feel internet access, like the "free" breakfast, should be bundled into the room price.
This variability is why I maintain a national dial-up service as backup. I hate that.