Is it more important that a worship service be contemplative or instructive, and how do we know? Per this link, there is a very definite effect of technology in worship.  

The benefits of using, say, an iPad to reference Scripture and all of the additional source material (commentaries, interlinears, etc...) are fairly straightforward - the pastor can teach, and leave as an exercise to the "student," finding the resources, etc... needed to back up an presentation. Additionally, if the preacher references "Balaam" or uses a word like "eschatalogical hope," it is beneficial if people can look up that term.

On the other hand, if the point of a sermon and or a worship service is simply to bring about a contemplative mental state, then these distractions (e.g. the lights emanating from the device, the temptation to go to non-church resources) would most likely outweigh the benefits.

So, how do Christians even go about answering what the purpose of the worship service is, in order to decide for themselves if i-Paraphenalia is to be encouraged or discouraged?
I think the real question is what God wants out of worship.  In Amos 5:21-24, God clearly tells the Israelites that He hated their worship.  This was worship He had commanded that they were doing.  I think that the real issue here is doing what God wants in worship.

I believe that iDevices can be a help.  I am a very old fashioned and conservative (Reformed) Christian and I use my iPad as my Bible in worship.  However I use it basically the same way that I would use my Bible, to read along with the pastor as he is going through passages.  When the minister preaches it is a holy event.  Hebrews 10:14 states, "How then shall they call on Him in whom they have not believed? And how shall they believe in Him of whom they have not heard? And how shall they hear without a preacher?"  The Greek does not say 'whom they have not heard about?' as some translations have it, but as the NKJV translates correctly, 'whom they have not heard?'  And Christ being heard here is directly related to the preaching of the Word by a preacher.  So when I am listening to a sermon I am listening for the Words of Christ.  I do not believe that every word a preacher says are Christ's words to His people (He would then be inconsistent) but that the Words of Christ do come through His ministers to His people.

So if I am sitting in church fiddling with my iPad and looking up some minor point (out of pride) to bust the ministers chops after the service, or if I am distracted by my device then I think that I have totally missed the point of why we are there.  We are in Church to give glory, worship and praise to our God, and to hear His very words from the minister.  I think this is the real issue.  

So if you can use an iDevice in worship to give greater glory to God then do so, if it is a distraction or point of pride, leave it at home.