Well, as already explained, in normal case when the device is idle (=no buggy software hogging cpu) it goes into same mode as s2ram automatically so you won't gain much with explicit s2ram. Many other devices implementing 'real suspend' won't last even 30 days suspended like N810 does when idle.

Also since the watchdog cannot be stopped you need to wake up once per 63 seconds anyway so real (=uninterrupted) suspend is hard to do.

BTW, maybe instead of pausing kernel for 60 seconds it could be enough to send SIGSTOP/SIGCONT on device lock/unlock to all PIDs not on some whitelist (or at least on some black list - browser and hildon-desktop are good candidates). That could have similar effect without some ill effects of suspending kernel.