From the discussion so far, this is still the best deal in these scenarios:
1. Travel internationally for a few days. How many days depends on your preference. There is cost to finding, buying, activating a local SIM card. If the cost of a local SIM and the value of your time is greater than the cost of this $2/day or $10/day over your trip, then this is the best deal.
2. Travel to multiple countries in a trip. The more countries you need to visit, the better this becomes.
3. Keeping your current # and plan active all the time during travel. This is important for those of us who need to still receive business calls, or any other must-answer calls. It can matter for those using sites or apps that require 2-factor authentication to your non-GV cell phone #. BTW - Google Voice #s won't ring your phone when you are on a foreign SIM, so you're not going to receive calls. Making calls would be OK with GVoice.
This seems to always be the best deal if #1 is the only issue. However, depending on how much #2 and #3 matter to you, this can be the best deal for more cases.
If you're already a T-Mobile subscriber, then their free 2g (and maybe 3g?) service may be sufficient for you. If you're not a TMo subscriber, it's not worth switching carriers for an occasional international trip.
btw - I also noticed that some countries (someone said Colombia) don't allow foreigners to buy local SIM cards on a local carrier. Their laws/regulations require you to be a resident and show local income. That would eliminate the local SIM option.