I still put the Marriott site ahead of Hyatt. The Hilton website has gotten much better in the past 3 years, although they have more downtime than the Marriott one. I don't use the SPG one enough, but it seems to me that Marriott's website is slightly better than SPG. The sad thing is that Marriott website was once the best one by far for hotel chains.

I have more of a timeout issue when I use Marriott's mobile page. I also find Marriott (& Hilton) have webpages that load the roomkey page too quickly when I am searching for a room on my iPad. I only get the roomkey page on my laptop if I get close to making a room booking and decide not to complete it. Roomkey, however, appears often during the middle of a search on my iPad, and it ends up taking over the page that was displaying my room search on Marriott & Hilton.