Peart is obviously an extremely skilled drummer, but I like the drum solos that carry rhythm or better practically an entire song. In that solo he plays a few things changing up doing different things. This solo sounds more like a skills display rather than anything of musical quality.
I guess you could say he was playing "off the cuff", but the guy has been playing for year and years and years. I'm sure he has something of musical quality he could have played rather than just putting his skills on display.