My gf has Yahoo messenger installed on her iPhone (3G) and I have it on my BlackBerry, which is one way to keep in touch (we live in different cities).
Has anybody experienced their iPhone becoming very slow (e.g. responsiveness) when running Yahoo messenger on it? I installed it on my iPhone (3GS) and didn't have any problems. It seems when she signs out of Yahoo the phone becomes slightly faster, but not by much. I haven't tried a restore yet, but will do so for her in June. Might this solve the problem?
On another note, I came across another IM client called Whatsapp, for iPhone and BB. Anybody tried it? I'm willing to give it a try, but it seems you have to pay a (low) annual fee. Also, their website doesn't make it seem like they're a very organized outfit!