Is it tremendously hard to integrate the people picker into an infopath form? NO!
It is not obviously easy, but can be done in a few steps, especially once you realise that it is called Contact Selector in Infopath and not People Picker!
These are the three main steps needed to add a people picker to your infopath forms:
Step 1: Add Contact Selector ActiveX control to Infopath
Step 2: Configure the data source to store the people data
Step 3: Add a secondary data connection to SharePoint
Optional Step 4: Configure the form for multiple Pickers
Okay, before we get started on the first step BE VERY CAREFUL with following the instructions. One click to many, one step skipped or preempted can cause a headache to clean up. Once you add the control to the page with an invalid configuration it is better to scrap the control all together and start from scratch. trust me on this one.
Step 1: Adding the correct ActiveX Control to the Toolbox
First you need to open the control box in Infopath

Next make sure to un-tick the Automatically create Datasource tick. THIS IS IMPORTANT. before clicking the Add /Remove Control Link

In the dialog that opens click add

And Choose ActiveX Control

Then find the Contact Selector in the list

And make sure not to include the cab file

Select Value as binding property

And choose Field or Group (any data type) on the Data Type options.

Step 2: Configure the Data Sources
Starting with how the control will save its data, you create a new group for your field, in my case it was manager and create a repeating group called Person beneath it. This repeating group has three simple text based child nodes called DisplayName, AccountId and AccountType:

Step 3: Next we need to set up the connection to the SharePoint server so we can look up people in the picker. To do this we need to create a xml file which will hold very simple connection data:
Create a xml file called Context.xml with following contents: <Context siteUrl="http://[your sharepoint server name goes here]"/>
Make sure your XML is well formed (closing dash and the likes)

We're nearly there... Now we need to import the data connection

as a Receiving connection

using XML data as our source

and specify our Context.xml file as datasource

That's it folks. Now you can add the people picker onto your form. The easiest option is to click anywhere in your document, open your datasource menu and Add the field as a Contact Selector to the form
