[Users] questions about OPENSER and Asterisk integration

hi, i have some basic conceptual questions about integrating Operser with Asterisk. Most of the examples I have read about so far talks about using asterisk for voice mail but can the integration also cash in on the other asterisk features? The examples always make reference to using asterisk to call out on the PSTN. I would assume that calling in on the PSTN and calling in/out on IAX channel would be equally viable but would it also make sense to use it to call in/out via SIP? my questions stem from my desire to utilize a lot of asterisk features because I just don't know openser well enough to start writing bespoke scripts. Stated another way (I did own up to the fact that I am no Openser guru) I would like to utilize all the work I have already done with asterisk and frontend it with the openser. Thereby having asterisk doing the typical softswitch work (call waiting, call forward, privacy manager, follow me, queues, conferencing, voice mail, etc) and openser doing the SIP proxy and NAT traversal capabalities for the UAs. thanks