I don't often worry one way or another about cellphones. We all have our favorites. That said, based on my experience, I strongly feel its worth mentioning that as a cellphone (talking), the One X has serious issues.
Unless you are always under very good to excellent signal conditions, the phone/network part may not work as desired. This ranges from dropped calls, unintelligible calls, lost connectivity to the network, etc. When severe enough, it does not reconnect to the network without the user manually going in and out of Airplane mode or even a needing a reboot.
After struggling with a second phone (and second SIM card), going through multiple soft boots, hard boots and so forth, it was apparent to me that I could no longer live with the situation. (I had to have a phone I could rely on!) It was clear to me that another One X (or SIM card) was not going to help.
Although it cost money to correct the problem (I was past my 30 day new contract period), I switched to a different phone (I reused the 2nd SIM card that was in the 2nd One X.) Night and day difference!! Places where I had no signal, I now do. There are no dropped calls. Connectivity to the network is stable. No need for reboots to restore connectivity.
While a software or firmware update might be able to cure these issues, none exists yet. So if you need a smart phone that works well as both a phone and a mini computer, look elsewhere than a One X! (or at least until they fix it!!)