It's all very well saying they're for use at quiet times, but a Pacer is not something that your average heritage railway visitor is going to want to pay to travel on. A 142 with bus seats and no tables is frankly not going to cut it, and will likely put visitors off from wanting to come again.
I have to agree. I think the problem with pacers at the moment (and this goes to any recently withdrawn stock) is that they are still too fresh out of service. Heritage railways attract some visitors (I stress 'some') so people can sample stock from several generations ago (the history buffs), or because of nostalgic memories from their youth. I'm sorry to say that even for myself (someone who likes pacers and see the future historic value in preserving them, same with HSTs etc.) would be equally disappointed if a 142 was running all the services, or the loco hauled stock was all air con MK2/3s. It just all so modern and like something I could have travelled on only last year.
Once we are 20 or 30 years into the future, the appreciation of them will be much greater and their place in history will be much more obvious. Future generations will be glad we saved them. The old saying, familiarity breeds contempt. How many people felt the same way about class 47s or class 50s in the 1970s? Or all those great Victorian/Georgian public buildings that were cleared to make way for the progressive 1950s/60s concrete office blocks?
As a side note, I really don't get the obsession amongst the railway buffs for tables on trains. The last thing I want on public transport is spending the journey sat in the aisle seat opposite some complete stranger wondering where I should look? I avoid the bay seating or table seating where possible. I Much prefer airline seating. This is probably why I'm disliking the 195s so much, the airline seats are so few and so hard to get. I'm missing pacers already.