True... some movies have a high MSRP and a low street value... but there are many with a high MSRP and a high street value. For example Lawrence of Arabia limited edition is $27+ at most places... you can effectively grab it from CH for $10 delivered.
The fulfillment titles are where the MSRP is important. The thread is really telling you to take high MSRP titles for the enrollment, and save your low MSRP choices for the fulfillment selections. If you don't want any $19.95 movies, than you will end up paying more total for the deal. But I usually need to buy one or two fulfillments and have no trouble finding titles I like for $19.95 (the minimum fulfillment price). What the thread on DVDtalk is saying is that it would be silly to take two $20 MSRP movies for your intro, then buy two $35 MSRP movies for fulfillment... it would defeat the hot deal.
All in all, I find this much easier than most hot deals listed here... where you have to PM, use a competitors coupon, send in MIR, then sell half of it on Ebay to recoup $$$. The CH deal is straight up, no hassles... you just need to research the MSRP of the DVDs you want in order to maximize your $$$/DVD ratio.
Bottom line: if you can find two DVDs you want at the $19.95 MSRP, then you can get 5 more at any MSRP while still averaging less than $10/DVD for all 7 DVDs. Simply sign up, pick your 5 DVDs with high MSRPs, then when it comes time to pay the piper, buy your two $19.95 DVDs, then cancel your membership. You can sign up the next day and do it again. The number of DVDs you have to buy at $19.95 vs the number of intro DVDs at any MSRP varies with the different codes listed on DVDtalk. Usually there is one promotion code that is obviously better than the rest.