I believe exactly what the Bible says in the whole book of I Corinthians 14. Everyone who is reading this right now should pick up their Bibles and read it!
I Cor. 14 is basicaly saying that there is really no reason for it and here are the reasons given:
When we worship as a congregation we are doing it for God, yes, but also so that those around us will be beter able to uplift Him in prayer as well. (vs.16 & 17--"If you are praising God with your spirit, how can one who finds himself among those who do not understand say "Amen" to your thanksgiving, since he does not know what you are saying? You may be giving thanks well enough, but the other man is not edified.)
Unless it is being interpreted so that the church (vs. 12--"Since you are eager to have spiritual gifts, try to excel in gifts that build up the church" ) and the person praying (vs. 14--For if I pray in a tongue, my spirit prays, but my mind is unfruitful.") can have a reason to be built up, then there are more important gifts that should be used. (vs. 19--Paul says:"I would rather speak 5 intelligible words to instruct others that 10,000 words in a tounge.")
The "tounges" is not what God wants to be emhasised, but the prophecy. (vs. 23-25--So if the whole church comes together and everyone speaks in tongues, and some who do not understand or some unbelievers come in, will they not say that your are out of your mind? But if someone comes in while everybody is prophesying, he will be convinced by all that he is a sinner...he will fall down and worship God"
If it should be done at all, then rememer that God is a God of order (vs.33--"For God is not a God of disorder, but of peace.") and therefore, only a couple of people should do it during a service (vs. 27--If anyone speaks in a tounge, 2-or at the most 3-should speak one at a time"), and it should only ever be done if it is interpreted for the people listening (vs. 27 & 28--"...and someone must interpret. If there is no interpreter, the speaker should keep quiet...).
Hope that gives a clear picture of where I stand on the issue.

I have been in only a couple of services where there was speaking in tounges. The interesting thing for me was that I was just interested in what was going on around me and therefor distracted from praising God myself. My husband on the other hand for some strange reason known only to God fallen asleep (literally!) and missed it all, and my (teen-aged) sister who didn't know much about it at all got very scared. I don't think it was of any use, just as I Cor. warns about. After all of this, I have to say that I actually believe the "gift is now used in the way of people actually learning and translating in different languages for the purpose of reaching others for Christ in a language other than thier first.---Anyway, my 2 cents.