I think it's a good thing that XCP is on Bitcoin, even if the blockchain may be somewhat hostile. In ViaCoin, there is a conflict of responsibility because the developers both maintain the blockchain and the the meta layer. The conflict of responsibility arises in that the blockchain developers must maintain as a priority the security of the blockchain. So in this sense of BTC vs XCP, it's healthy.

IMO when assessing a metacoin, people should assess the liquidity of the underlying blockchain as an indicator of potential success of the metacoin. The inflows into the metacoin will come almost exclusively via the blockchain it rides on. There isn't much point having a technological marvel which is in an isolated island.

In terms of technical features, it's great that Peter Todd has the funding to work on tree chains. If it proves to work well in ViaCoin, there is no reason why it won't be integrated into Bitcoin core.