Carriers are well known to tightly control their mobile phone offerings.
Optus is no exception to this point.

I recently started using a PennySIM service. Previously I have been using Exetel. Both are Optus 3G resellers, but Exetel seems to have its own infrastructure and internet access and APN for their HSPA connections, whereas PennyTel use Optus Infrastructure, including APN’s, SMSC and MMS gateways.

Since getting my hands on an Android phone earlier in the year, I discovered I had no access to paid apps in the Android Market.
I only ever saw Free apps in searches.

After doing a quick search I discovered I was not the only person to notice this, and many had proved that it was an Optus only issue.

Here is a link to an article describing the problem:
http://apcmag.com/optus-deliberately-blocking-android-paid-apps.htm

Last week whilst browsing the Android Market, I noticed apps with prices appearing! A quick search confirmed Optus has indeed officially acknowledged Apps were blocked and have now unblocked them:

We’re very happy to let all our Android customers know that you now have access to all paid apps in the Android Marketplace.

http://apcmag.com/optus-unlocks-access-to-paid-android-apps.htm

Another issue which I only found when switching over to PennySIM is that m.google.com, Google’s mobile app portal was blocked by Optus (this was verified by using Exetel or Telstra service to connect to this portal).

This means I have no access to Google Wave and other cool Google apps.

This link to whirpool shows other users having trouble with m.google.com site. ( http://forums.whirlpool.net.au/forum-replies-archive.cfm/1371671.html )

I will be contacting PennyTel and Optus about this issue.