IMO I think an APAP is good and far more useful than a CPAP. For one thing an APAP can run in CPAP mode and be used that way. Another important factor is that you have data from each night's sleep that can reveal how you are doing, sleep wise, when used in the automode. Of course this data will be no where near what an actual sleep study gives but still is an accurate record of the data you want to know about. As anyone on OSA treatment knows certain sleep positions require certain pressures to keep OSA at bay. For example, sleeping on your back (the position most apt to create OSA) will require a higher pressure to keep the tongue from falling to the back of the throat (which would create an OSA) than say lying on either of your sides. Therefore, if your 2nd sleep study only accounted for a pressure setup while sleeping on your side (no pressure setup for back sleeping) then you could still have an OSA event if you were to end up sleeping on your back (not a good situation)

. Furthermore, if you were sleeping on your sides more than you sleep on your back, why would you want to have the extra pressure exerted on you when an APAP would adjust down to a lower pressure that would still keep your airway open. The adjustment down could be as high as 6cm H2O drop.

Wow!

Some people tend to adjust better to an APAP than a CPAP yet for others it is the direct opposite. Sleep studies do have the tendency to give a pressure setting that may not be quite correct for you due to a different sleep environment then what you are use to, uncomfortable (resulting in poor sleep) due to the wiring up of your head/body and possible introduction of a sleeping pill which would have the tendency to relax your body even more than normal. An APAP would account for this because the settings would normally be 1 to 3cm H2O lower than your titrated value and 3 to 4cm higher than the titrated value. Finally, if you purchased an APAP that your sleep doctor uses you could easily either hand the raw data off to him or sit down and discuss the compiled data thus allowing you to participate in the making of decisions in your treatment.
I agree with the others when they say the mask is the most important factor. If the mask is not comfortable and one you can sleep with then your compliance to this treatment will be nil.