TeamViewer works wonders, no need for signing up/making passwords on goofy 3rd party sites (it does make both devices have a code you have to put in, like Bluetooth). And it's pretty fast/works anywhere (also works on 3G I think). It is battery draining though.
I haven't tried Splashtop yet, but I have it (free from Getjar).
I use Android VNC and Team Viewer a lot, particularly TeamViewer.
TeamViewer has been invaluable for me in my line of work, I have around 20 servers/40 desktops around the country setup with it. The ability to remote into a system from anywhere and not have to have a static IP or remember a code or domain name and port is fantastic. Even the Community Build Server uses both VNC and Team Viewer to control it when needed.
How long is the time between something come up on the screen and it showing on the phone take you?