1. Load Time
As there is redirect involved , there will be some extra time taken at the user-end. After rigorously testing it with GTmetrix ,it averaged around 1 second. Here is a picture describing it
As the URL changes , the person visiting the blog might not either be able to notice it or think there is something sneaky with the site. If the person does notice it ,another effect can be the less likability of clicking it again.
This is a multifaceted thing. There are lots of angles to it.
<b:include data='blog' name='all-head-content'/>
There is no effects on the Search Engines evaluation of your blog as the presences of the Canonical tag nullifies the effects of the Redirect.
c) Country specific problems
As ccTLD's were introduced to make it easier for Governments to ban a blog in their region ,this might become a problem. I started a thread in the Google Webmaster Forum, and here are some of the replies:
An Level 11 moderator replied to it and slightly suggested that Google might not like it. You can also drop-by and voice your opinion on the thread . Here is the Link
4. Alexa Ranking
This is the biggest plus of using the Redirect script. As all traffic is channeled to .com domain, the Alexa ranking remain consistent all throughout. As the rank is not distributed between country specific URLs, its easier for Alexa to estimate your rank correctly.
All-in-all the Redirect Script has a positive effect on your blog. Rest we will see as it unfolds. Have you experienced any thing unusual while using the Redirect, feel free to share it.