The CRM development team at Microsoft slid in the Microsoft Dynamics CRM Mobility option called Mobile Express a while ago - (I could even say years ago -Check out Settings, Mobile Express) and as far as I can see they have been updating it little by little as the rollups and new versions come out.
What does this mean? It means that Mobile Express is an option worth checking out, BUT that it does not necessarily meet ALL your extensive mobility needs depending on what you need in a Mobile client and what and how many platforms you need it to run on as well as how many extra mobile specific features you want.
The mobile ISVs including TenDigits and CWR Mobility are totally focused on working with mobile teams to empower them and encourage them to get more from their Dynamics CRM Investment. They also have additional features that are integrated so if you need those additional features get the teams at CWR and TenDigits to give you a demo, BUT if you just want to access Dynamics CRM from your cell phone once in a while then take a peek at Mobile Express.
Of note Mobile Express is a Free feature in Dynamics CRM and yes, there are a number of people who don't realize this. Pay to get it configured and to learn the best way to use it from your partner, but don't worry about extra licensing fees.
Articles on Mobility and Dynamics CRM are as follows: