Is using HTTP 1.0 bad practice?

Question

I'm implementing a basic http client for communicating with a web service and am wondering if I should go with http 1.0 or 1.1. The data section will consist of binary data and the remote server will always be controlled by me (running IIS7.5). The firewalls / proxies inbetween is nothing I'm controlling, ie. the packets must not be stopped if wrong http version is used.

I've been reading up about the difference between http 1.0 and 1.1 and it seems to me that http 1.0 supports everything I need.

Will I encounter problems if i choose http 1.0 over 1.1 or can I assume that everything will work just as good?

What makes me wonder is that if I connect via raw sockets to IIS7.5 and send a http 1.0 get request, the response is always http 1.1.