They sound great. I also have a Pioneer RT-707, and even with just good quality needledrop tapes (7.5 IPS quarter track Maxell UD 35-90, good for two 1970’s era albums per reel), there’s a warmth and organic flow that vinyl alone can’t quite match. The top end is rolled off, and of course the noise floor is much higher - but that stuff in the middle...is magic. Playing these tapes is the only time I’ve consistently liked the Tannoy supertweeters, but it still sounds amazing without ’em too. I find the supertweeters way too "hot" for vinyl playback with MC cartridges (even loaded down).
I’ve heard the $500 a pop modern audiophile reel tapes, backed by lots of expensive kit (high end J-Corder Technics deck, Doshi Audio tube head amp), and yes they’re truly State of the Art (no HF roll-off, lower noise floor). However, that route is a no-go for me due to high cost coupled to poor availability of material. I just play my old needle drop tapes as an occasional treat :)
The "warmth of vinyl" reputation really belongs to tape. I have had (and still have) lots of high end analog gear, which I still love too - just saying, I’m not comparing this tape to a Fluance. The best Koetsus get very close to this midrange magic, but good tape still has more of it.