Growing interest towards cloud application platforms has resulted in a large number of platform offerings to be already available on the market and new related products to be continuously launched. However, there are a number of challenges that prevent cloud application platforms from becoming widely adopted. One such challenge is application portability. This paper reports on an ongoing effort to explore the area of cloud application portability. We briefly examine the issue of heterogeneity in cloud platforms and highlight specific platform characteristics that may hinder the portability of cloud applications. We present some high level approaches and existing work that attempts to address this challenge. In order to narrow down the area of our exploration we have been carrying out an experiment in cross-platform application development and deployment with four prominent cloud platforms: OpenShift, Google App Engine, Heroku, and Amazon Elastic Beanstalk. We briefly discuss our initial conclusions from this ongoing experimentation.