I have a pretty large collection of Postscript Type 1 fonts as well as a few in Type 1 Multiple Master format. Quite a few of those old fonts still get frequent use. Take Akzidenz Grotesk for example. Illustrator 4 included much of that type family as well as some other Berthold faces. I don't care so much if they're in True Type, Type 1 or OpenType format. It's just pretty handy having some of those old Berthold "BE" faces.
I do prefer OpenType quite a bit over "legacy" Postscript Type1 and TrueType formats. But I'm not going to buy Akzidenz Grotesk all over again just so I can have it in OpenType format. It would take a very serious, very specific customer need to justify such a purchase.
If I'm buying a typeface now, I'll certainly try to get it in OpenType. Additionally, the extra OTF features like extended character sets, multiple language support, fraction numeral sets, etc. will increase the value of the type purchase.
In the end, those new OTF typefaces are going to live side by side with the T1 and TT fonts I already use. With what I do, all the type often gets converted to outlines once I'm finished with the design anyway.