I jumped on the Global Plus the day it was announced (Nov 9th). Luckily I got myself grandfathered into unlimited high-speed plan. So far I'm loving it. Yes it is expensive, but to me not having to deal with the hassle of daily passes or 10-day passes is worth it. Also, way easier than tracking down local sims.
Before jumping on this I had been using Project FI. Which BTW just announced that you can now use on non-google phones like iPhones. Even though I now have the grandfathered unlimited T-mo plan... I'm very tempted to port my main number back to project fi now that I can officially use it w/ my iPhone.
With T-Mo...I'm paying $120/ month base for my wifes line and mine. If I want Global Plus on both that is another $50/month per line. I rarely use more than 12GB a month. On FI, this global full speed access would come to at most $80/month / line. Whereas on T-Mo we are talking about quite a bit more. This month has really been very exciting for us global roamers.