I just bought dmc-tz15 2 weeks ago and able to "abuse" the camera on my holiday trip to Hongkong last weekend. (took over 500 pictures and 2 video in just 3 days 2 night trip
My opinion :
If you don't mind being slightly bulky then fx500, the 10x zoom is a must have for travel needs and you will be glad that you had bought tz15. Although fx500 wide angle is slightly more then tz15 but 28mm is already more then enough for general purpose.
Take a look at few of my photos that i've posted in flickr
or u can find my user name "Bong Teo" in facebook acc. (there's 4 ablum of photo and 2 video, all were shot using tz15)
Those pictures that i've posted will let you visualise how far is 10x able to zoom in and some comparision between night scene shot, starry sky shot and manual shot of the beautiful Hongkong city @ The Peak.
As for the full manual control, i guess it won't help much if you want to take pictures in a pub/party cos most probably you will be setting the camera in auto mode.
As for full manual control for night shots, i would think tz15 would do a nice job confidently as long as you play around with it's built in settings.
Hope all this can clear your doubt
If happen that you have a facebook acc and had already watch my video which i took it in Hongkong disneyland, that is a bad example cos i never realise that i've adjusted the exposure to max!!
Btw thank to this wonderful website and forum, learn alot of thing about camera.