Are PCC189/7ES8 tubes useable in place of 6DJ8?

I've seen old stock tube dealers on Ebay claiming that the PCC189/7ES8 can be substituted for 6DJ8s as a drop-in replacement. I've also read that this shouldn't be done.
Does anyone here know, for sure? Any experience? Thanks!
As you've found, there is lots of conflicting advice out there. Here is one of the more negative opinions:

I note in my tube manual that the 6DJ8 is listed as having a nominal u (amplification factor) of 33, while the 7ES8 is listed here as having a nominal u of 65. Perhaps operating the 7ES8 with only 6.3 volts on its filament, as opposed to the specified 7.6 volts, would bring those figures closer together. But I would not expect anything better than a rough approximation, which at best would be good enough sonically only in some circuit applications.

-- Al
From AA also.
Posted by Eli Duttman (A ) on July 30, 2006 at 10:17:47
In Reply to: PCC 189 a replacement for PCC 88? posted by uwe on July 30, 2006 at 09:30:19:

The ECC88 = 6DJ8. The PCC88 = 7DJ8. The ECC189 = 6ES8, which is a variable mu (gain) type. The PCC189 = 7ES8 and it is NOT suitable for audio service.
AI preamps are notorious tube eaters, as your experience indicates. The "best" tube for service in your unit is NOS Russian 6n23p-ev. The Russian NOS is TOUGH and has decent sonics.
Hhmmm.... That's about what I thought. I've been using the PCC88/7DJ8 with very good results as an alternative to my Ediswan 5358s when I want more extension on top. It's just that the PCC189s are sooo cheap on Ebay. It's hard not to try them. Thanks guys for the input. Much appreciated.