They're noisy and lo-fi. They have an abysmal reputation for breaking down. And the damn tape cartridges are rarer than hen's teeth. But I'll have to say I'm quite smitten with the Univox EC-80 and EC-100 Echo Chamber units I recently acquired (for far less than the average boutique delay pedal). Got 'em both for less than $250 (combined).
However, neither were sold in 100% working condition, so I had to do some research and repairs to get them back up to snuff. The EC-80 was actually in good shape, the tape in the cartridge just sucked. The EC-100 passed clean signal and was mechanically functional, but there were no repeats. Turns out there were several problems, not the least of which was a dead playback head. I snagged a cheap tape deck from Salvation Army and pulled the head from that. Now the EC-100 is working normally again.
The rare-ass cartridges are old Dictaphone type. They are basically exactly like 8-track tapes but with 1/8" tape instead of 1/4". But you can take PlayTape tapes and use those instead, and they are way easier to find (and cheap). The PlayTapes do not have the same side groove as the Dictaphone tapes, so they don't fit in the Univox. So I modified the Univox cartridge housing (cut out the stupid little notch) and now the PlayTapes fit. Sweet.
Here's a pic of the EC-80 :
Expensive-ass cartridge opened up:
Here's the EC-100 out of the box and with a PlayTape:
Here's PlayTape vs Dictaphone:
Here's a shitty clip of the EC-100:
[soundcloud]https://soundcloud.com/effdub/univox-ec-100-with-playtape[/soundcloud]
That will be even cheaper than buying new carts.