I have a TEAC X-1000BL deck that I've had since new. I have a modest collection of prerecorded tapes (rock) and I have dubbed several box sets and albums of classical music to 10" tapes. This machine is selling for more than I paid for it (not adjusted for inflation) so it's interesting to see this format come back.
Even though I don't listen to it very often I love the look of it and I can't bear to sell it. Regarding the SQ of the prerecorded tapes, the 7.5 ips tapes sound much better than the 3.75 ips tapes. However, there is noticable hiss and the quality of the sound is so-so compared to a CD. In my experience a 7.5 ips prerecorded tape is about as good as a quality vinyl pressing of the same title. I have a high end digital rig and to my ears neither vinyl or tape can beat a CD.
My deck has DBX noise reduction and it can use high bias tapes like Maxell XLII. I have a Burwen Transient Noise Eliminator (removes the ticks and pops) that I used when recording the vinyl albums and the result is amazing. The taped album is virtually a perfect copy of the record without the ticks and pops.
Using a R2R is somewhat like playing vinyl in that there is a ritual to getting it set up and you get the satisfaction of seeing a finely built machine in motion. I have heard several 15 ips machines at audio shows and I would love to have one but I can't justify the expense. But once in a while it's fun to put on a Led Zeppelin tape or listen to Beethoven's 9 symphonies without having to flip all those records over.