I use suspend as much (or more) because I want to keep everything open with the running state than because of the reboot time. For example, I often have a lot of emacs buffers and xterm windows, and I want that state preserved for as long as possible. I've been known to keep login sessions going for months on end.
With Session Manager, the Firefox annoyances aren't that big of a deal; it's the other stuff I want kept around.
Suspend/resume does not eliminate the need for faster boot time, or vice versa.