All in all operating PSK31 on the Icom 7800 is quite a pleasant experience. As noted previously, the built-in software may not have all the features of external software - particularly substitution macros for stored messages and auto-logging, but it does a fine job at the business end of pulling the signal out the aether and of basic message transmission.
One question that's currently dogging me though is how to scroll back up the message buffer in the 7800's PSK decoder to review the QSO. I'm still a bit fumbly operating at the moment, and managed to forget another stations call after he sent a long 'brag' message. I simply wanted to scroll back briefly to remind myself of his call, but discovered that I didn't know how to do this! The manual is quite silent on the subject in both the RTTY and PSK31 sections, though it's possible that scrolling is a general feature that is dealt with somewhere in another part of the user manual (though I've been through this several times now for general background).
I'm assuming this is possible, but I just haven't figured it out yet. I shall ask around on some forums and check with my friend and Icom-expert Adam Farson. Without scrolling, I would certainly consider the decoder tool to be somewhat deficient - so hopefully it's in there somewhere!