I mentioned the tds220 on ebay because it's very similar to the tek in the two scopes for sale thread.
I used one of these for years at a job, and I *hated* it.
that thing takes a sample, and then just sits there forever (in electronics terms) crunching away, then eventually refreshes the screen, and then decides to maybe become ready to trigger again maybe a second later.. meanwhile you've lost 99.9% of the signal you're looking at, including the rare glitch waveform you wanted to see.. Oh and it only shows one capture at a time, then next capture the old is completely deleted..
of course being digital, you could try to capture a "wide" grab of a signal, and then zoom in to look at it and hope something happened in the longer capture.. but TDS220 has so little memory depth that this feature is useless.
I spent the whole time I was using it wishing I had an old analogue cro that had decent retrigger time.
Newer TEKs (TDS3000, which was actually the serious scope at around the same time as the 220 I think, then the DPO, MSO, and now MDO ranges) got way way better at capturing without a giant pause, and even manage to keep previous traces on the screen as they redraw new ones. (Digital Phosphor is tek's marketing term here)
Decent newer cheaper scopes (like the rigol 1000z series I also mentioned a listing of) work this way too.
New ultra cheap scopes still work like the tds220, and as far as I am concerned, may as well be landfill, because they are not useful for real work.You are better off with any old CRO in basic operational condition than a slow digital scope.