I routinely use a matched pair of 8020s spaced at 28.5 cm as outriggers with a pair of NOS 8040s for classical chamber music ensembles. I've produced excellent recordings with this combo in various locations ranging from very dry to very reverberant. The 8020s blend very well with the 8040s and I'm generally quite happy with the sound.
However, I have had reliability issues with the 8000 Series mics as many users have had. Both the 8020s and the 8040s developed the intermittent low-level noise problems that have plagued the 8000 Series. I sent both sets back to Sennheiser USA and they immediately replaced the 8020s and sent the 8040s back to Germany for repair. Since then (over one year) they have all worked fine, but I still don't have 100% confidence in the mics, so always bring a set of "back-up" mics on any job.
I love the sound quality of the MKH8000 Series mics when they work, and sincerely hope Sennheiser actually has found the source of the intermittent noise problems. Only time will tell.