Ros,
I think the key point is to buy good quality branded tape then stick with that brand. As Paul says, the tapes are quite cheap so if you use them once and keep the original as an archive you can always go back and re-deit the source material once high-definition playback devices are more readily available at sensible prices.
Practising what I preach, I have the Sony HVR-A1. I use Sony tapes, record on them once only in HD, downconvert in the camera to SD, then file the source tape. By using the tapes once only, the potential for drop outs due to tape wear are minimised.