have not heard of vibe, but it seems from the way you describe it that this “friend” is your girlfriend/boyfriend? or maybe bff? if so, and they are out and about more often than they are at a place that will allow you to skype/gtalk, then going with vibe may be worth it.
the one thing to consider is that with a contract and a real data plan (ie: all you can eat) you can get pretty well subsidized phones with any of the big three carriers. as an example, you can get an iphone, android or even n97mini for pretty cheap with a contract vs a sim-only plan when basing the calculation on total-cost-of-ownership of the contract for the 2 years.
the other thing to consider is that the “big screen” phones can be an unbelievably good resource for learning taipei and even more so, learning chinese.
not sure how proficient you are with chinese, but i had zero when i got here and the phones have helped me a ton. i use my phones, for example, to insta-translate stuff i need to say using google translate, hangpingdict and plecodict. or to practice handwriting chinese characters. both android and iphones sold here have chinese handwriting input, so you can force yourself to practice or to learn a random character you see on the street. i have a pdf of the practical audio video chinese book and the audio on my phones so i can read and listen where-ever i am whether it’s a coffee shop, at the mrt, etc.
i also use them to find a great place to eat that is not obvious (using layars and foursquare).
being in a new place far away from a large chunk of your friends for me is also made easier with stuff like facebook, twitter, gtalk and even games like words-with-friends.
btw, all these phones apps were free.
one of the inexpensive android phones might be a great bet for you. examples include the htc tattoo and the taiwan mobile t1. with a well worked out contract and TCO calculation, you might be able to even get one of the higher-end android phones for a great price as well.
also, i should note, i have a prepaid sim on chunghwa (senao) and a iphone+sim contract with taiwan mobile (myfone) and i will say that the coverage and download speeds on taiwan mobile are pretty damn good. if you get an all-you-can-eat data plan, and get a phone you can tether to your laptop (android is easier for this), and you don’t do stuff like torrents, you may even be able to get away without land internet.
i have actually NEVER been ANYWHERE in taipei where the phone didn’t work, including MRTs, the middle of big concrete buildings, etc. i also have chunghwa for my land internet but i have forgotten what a land-line is.